# Hydra and Hydrogen Peroxide - My Expreriences



## dinokath (May 3, 2009)

Hi all,

Starting this thread primarily for the person who has a planted tank with snails and shrimp that recently received the gift of hydra and seed shrimp. Hope this helps! 

A little background - started paying closer attention to the tank recently instead of the cursory water change and regular feedings and bought some new livestock(about $250 worth of RCS, amanos, nerites and plants) about a month and a half ago. Everything was going well until I noticed what I thought was staghorn algae. Well, it wasn't, it was the beginnings of a hydra outbreak, I just didn't know it. In all my years in this hobby, I have never had the pleasure. I had planaria once about 10 years or so ago and treated with fenbendazole but have never seen or heard of a hydra. Mentioned it to my dad the other day, who got me into tanks when I was a wee lad and he went "Hydra? What's that?", which made me feel less stupid for just a moment.

I have read just about everything out there on hydra and how to control it. Everything from starve it to blast it with a syringe and H2O2 (more on that later), to betel nut extract to fenbendazole to flubendazole to potassium permanganate to manual removal to heating up the tank to 104+F for 4 hours to adding fish to eat it (not an option) to a whole tank H202 treatment. If there is something out there on hydra in a planted tank with shrimp, odds are I have read it in the last few weeks. 

So, going down the list of possible treatments as they relate to me and my tank:


Adding fish - no go. I have shrimp, lest they become shrimp food. Thought about the wee little raspbora as they are supposed to love hydra, but I just don't want fish, other than my otos, in the tank.
Fenbendazole - an option BUT it can harm/kill your nerites. JUST spent about $65 on a whole new crop of olive, zebra and horned nerites. This is my last resort, HOWEVER I did read someone post that the usual 0.1g/gallon for planaria can but cut in half for hydra to 0.05g/gallon and if all other options fail, this is the route I am going and hoping for the best.
Flubendazole - Can't find it in a cost effective format or without a prescription. The difference, I read ONE poster say, is that the *FEN*benzadole will bond to biofilm and make it poisonous for nerites for years to come where *FLU*bendazole will disperse in water and go away with water changes. I make no warranty on that statement, just repeating what one poster said on a forum.
Betel nut extract - goes by No Planaria and Planaria Zero. Totally safe for shrimp and fish and plants. Deadly to nerites. Bought a $26 bag of it before I read/realized it. It's in the closet waiting to be sold on no ebay links allowed
Potassium Permanganate - deadly to shrimp, snails and biofilter things BUT my course of action would have been to remove all the plants, give them a dip in a solution and return them back. Then I noticed it was growing all over the substrate. Sigh...
Heating up the tank to 104+F - Got a sous vide on loan from a buddy. If the H2O2 course ultimately fails, this is what I am going to do next, followed by flubendazole at 0.05g/10gal if that fails
Starving them out - Don't got the patience for this. 10 or more berried shrimp and I don't want my babies to be hydra snacks. 
Manual removal - started here. Cut all the affected leaves off. Didn't help at all, it would have helped had I done it from the start when I noticed one.
Blast with H2O2 in a syringe - this worked well at first. Then I noticed several dead shrimp and nerites and stopped. Turns out the stuff you buy over the counter in the brown bottle has stabilizers in it that are not good for your fish! *Never* read that before in all my readings on the stuff and using it to spot treat algae like BBA and cyanobacter but I will admit that my reading on the subject started and stopped right there. BUY FOOD GRADE H2O2. Readily available from the Interwebs. It's a bit pricey but keeping your end of the bargain and NOT killing your livestock is important, right?
Whole Tank H2O2 Treatment - now on to the whole reason for my post.....

Like I said, I have read everything on the first 15 or so pages of the Google Search "Shrimp Tank Hydra Removal" or "Treatment". Came across one article that details all the various ways to remove the hydra and how, most importantly, to prevent it in the first place. (LINK). In there was a list very similar to my list above. What intrigued me was the whole tank H2O2 treatment and the link to the video for Mark's Shrimp Tanks where he seems to regularly dose his tanks with H2O2 (the fragile CRS and bee shrimp BTW, not the hardy RCS I have) to keep them clean and fresh. Hmmm... Interesting! I am already $40+ in on this hydra eradication after the No Planaria and fenbendazole so why not order up another $15 bottle of 8% FOOD GRADE (*can I stress that enough?*) H2O2. Ordered it up and it arrived yesterday. 

I decided to move the nerites to another tank a few days ago just in case I would up going the medication route.

Mark's site is very specific - 3% FOOD GRADE H2O2. I had 8%, so I did the math and at 1.5ml/gallon of 3% FOOD GRADE H2O2, that came out to 43ml of 8% FOOD GRADE H2O2. Turned off my filters, kept my wave maker going and poured it into the tank. Moved the head of the wavemaker around to it would get to all the nooks and crannies on the other side of the tank. It took about 30 minutes for any kind of bubbling to start. It started VERY slowly at first, just a bubble or two after 30 minutes. During this time, I shifted the wavemaker every 5 or so minutes to keep the flow all around the tank and behind the plants and driftwood, where those little buggers REALLY took a foothold. The hydra, at this point, appeared completely unaffected. The shrimp seemed fine as well, in fact, like in Mark's videos, they seems a bit more active but it could have been all the shifting of the usual flow patters on the water, who knows. 

After an hour, the bubbling kicked up a bit but still had not hit the peak. I noticed some hydra, maybe 5% were balled up tight. Interesting. Another 30 minutes and the bubbling was really in full force, plant were pearling like crazy from the recently cut stems where I did manual removal, it was a bubblefest! At this point I kicked the canister filters back on. That's when things really started to take off. Over the next hour, it was a swimming display of bubbles and hydra in the water column. I mean there were hundreds floating around everywhere. The shrimp were going nuts playing in the bubbles, stunned and/or dead hydra were everywhere. I was amazed. Not all the hydra had broken free, I'd guess about 50% were still stuck to the glass, substrate, plants and driftwood and appeared unaffected. I would take my finger and poke the hydra floating around. Some would contract like they usually do when you touch them but most did nothing. After another 30 minutes, I couldn't find one in the water column that reacted to a touch. "Sweet" is what I recall thinking to myself.

I left it alone and went and made dinner at this point. After dinner, about 2 hours later, I came back and noticed not one single hydra had its tentacles out in the 'breeze' and all of them that remained attached to a surface were balled up tight. Dead? Meh, maybe? Stunned? Oh yeah. I'd guess about 25% of the original number of hydra were still stuck on something but the rest seem to have disappeared either into the *very awesome* Eheim prefilters I have installed or into the equally awesome Eheim skimmer. I dropped in a wafer for the shrimp to eat and they devoured it. Best I have seen this batch of shrimp eat ever. Went to bed at this point. Woke up and took a peek. Still roughly the same number of hydra attached to a surface, still none open, all balled up. No shrimp deaths, yet. None of the assassin snails appear to be dead either. Going to check parameters tonight for ammonia and whatnot. A tiny bit worried about the biofilter but it's probably just me. That Mark at Mark's Shrimp Tank really seems to know his stuff.

I am very optimistic on this course of action. I will keep up with this thread and post back as the treatment progresses. I am out of town all next week so I plan to do a 50% water change this weekend and, if I still see little balled up hydra, do another round of *FOOD GRADE* H2O2 treatment.

OH - the seed shrimp! So, apparently whatever brought in the hydra brought in the seed shrimp as well. I know they don't hurt anything and indicate good water quality, but I just don't want them in there. They look like little white fleas everywhere. Yuck. Apparently hydra will take care of them. So in letting my hydra get a little out of control, it seems to have helped with the seed shrimp. Where I saw 100's a few weeks back, in the last two days, I have seen not one. I doubt they got them all, probably hiding in the substrate somewhere waiting for the coast to clear, but one can hope! They seem to be VERY hard to get rid of so if they do come back, they may just be an unwelcome addition that I have to live with.


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## sumer (Feb 6, 2010)

Isn't it satisfying to watch them oxidize and wither away!
I wrote an article on this very topic and also recorded this on video- https://www.reef2rainforest.com/2015/09/11/silent-baby-fish-killers-freshwater-hydra/


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## en7jos (Jun 7, 2020)

Interesting write-up @dinokath, thanks.

I'm in a similar position with a hydra outbreak in my small RCS tank. Like you, I have a packet on No Planaria on the shelf as Plan B, but am hesitant to use it because of my snails. So trying to eradicate the hydra with peroxide, following on from the video posted by _Marks Shrimp Tanks_.

Really interested to know how you got on - can you post an update please @dinokath?

I did in initial 1.5ml / UK gallon treatment and was optimistic. Certainly did no harm, seemed less hydra about the next day, shrimp enjoyed the bubbles and it got rid of the green hair algae on my mosses. Great! But certainly didn't get rid of all the hydra. I've since tried a second whole tank treatment at about 2.0ml / UK gallon which also failed to get all the hydra.

Now I'm spot treating individual hydra when I spot them using a syringe and blunted needle. Doing this pretty much every evening and certainly seem to have got rid of the bigger hydra. But the more I look, the more small (tiny!) hydra I'm spotting! The tank has Amazonia soil and, although I have few on the glass now, there are lots of little ones (less than 1 or 2mm long) hiding in any amongst the grains of the soil.

My own conclusion so far is that the treatment was generally good for the tank (doesn't seem to have caused any issue, and has cleared green hair algae from moss) and has probably reduced numbers of large hydra out in the open. However doing whole tank treatment doesn't get to those that are hiding within the substrate. I have a feeling that the moment I stop spot treating those that I can see, the numbers will just increase again. 

So I fear that hydrogen peroxide is a good control to reduce numbers, but is not a way to eliminate hydra completely.

Interested to hear anyone else's tips, experience, successes or fails please! (But please don't suggest using dewormer or fish as non-starter for the reasons OP already mentioned).
Unless anyone knows of a small shrimp fry friendly fish that devours hydra?....


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## dinokath (May 3, 2009)

Yeah I should have replied back on this one. I was pretty pissed off and after reading below you'll understand why. Plus been slammed at work with the whole COVID outbreak so the tank has kind of taken a backseat lately.

I was meticulous about the H2O2, weighing it instead of measuring it to ensure the right percentage went into the tank, double checking and then triple checking the calculations, etc. It worked, for the most part, in controlling the hydra. What it did do was kill the crap out of my cherry shrimp. I mean a dead, mass extinction type of event. Went from 100+ to less than 10. The amano's fared better, which kind of surprised me in the long run, and I only lost 3 of the 25. Oh, and the hydra were still there, albeit in VERY small numbers, but still there. 

I wound up putting all my nerites into my daughter's tank and treating the tank with dewormer at 1/2 the rate of what you'd use for planaria, can't recall what that is at the moment, but that's what I did. I decided to let the assassin snails fend for themselves and as best I can tell, not one died. The really big ones are still there and there are plenty of wee little babies running around. It knocked out the remaining hydra and, huge knock on wood, they haven't resurfaced. I also went on step further and dipped everything in potassium permanganate, everything except the substrate and the tank equipment that is. 

I introduced a single nerite a couple weeks ago to see how it would do and it was dead inside 2 days so they will live in her tank for a while. In another couple months I will add another and see how it does. I have read the dewormer pretty much ruins your tank for nerites forever but we'll see. She likes them in her tank so there they will live for now.

Good news is this kind of pissed me off quite a bit and I have just left the tank, pretty much, untouched since roughly March 15, just over three months now. No CO2, no ferts, no nothing except mild light and feeding the remaining shrimp every other day. The cherries have rebounded very nicely and I am back up to at least 100 if not more and the babies that were born after the mass extinction are starting to show saddles. Algae is a mild problem at the moment and some BBA is starting to regrow but very slowly. I might just let it go for a while longer and see what happens.

Long story short - unless I really really really miscalculated somewhere and added WAY too much H202 to the tank, I don't suggest this as a way to eliminate the hydra.


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## faywayway (Aug 12, 2020)

I have a hydra problem starting in my tank and I really want to get it under control before their population explodes beyond fixing. My situation is similar to yours in that I have 5 green jade cherry shrimp that I got today from a shipment and have other amano shrimp and nerites in my tank right now. I was wondering if there could be a way for me to take out the nerites and shrimp and put them in their own containers, then add the hydrogen peroxide in small doses directly on the hydras. I have some questions to go along with this. It's totally okay if you can't answer, I've just been doing lots of research to no helpful answers.
If I were to do this (take the animals out while dosing H202), do you by any chance know when I could expect the H2O2 to be broken apart safely so I could add the animals back to my tank? 
Is this method safe for plants?
Did you keep your filter on, did the peroxide not damage the bacteria or in your tank? 
Again, if you can't answer these it's fine, I'm just desperate at this point as I've watched my shrimp get stung by these things and it's upsetting because I really like them plus they were pretty expensive. I just don't know what to do about this so any help or offering other resources I could check out would be greatly appreciated.


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## Tiger15 (Jan 7, 2018)

In post 1, OP was optimistic that H2O2 has probably wiped out all hydra. Then 3 months later in post 4, he was pissed off that the treatment had killed 90% of his cherry shrimp and a few hydra were still around. What has gone wrong?

The difference between medicine and toxin is the dosage. What dosage has the OP used. 1.5 ml 3% H2O2 per US gal or UK gal? Note that UK gal is about 20% larger than US gal.


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## en7jos (Jun 7, 2020)

Hi @dinokath and @faywayway

Here's my experience of getting rid of hydra from a shrimp tank:
https://www.plantedtank.net/forums/...iminating-hydra-shrimp-tank-success-last.html

In short, I found hydrogen peroxide (H2O2) perfectly safe for all my shrimp (both neo and caradina) at the 1.5ml per 4.5 litres dose recommended in the _Mark's Shrimp Tanks_ Youtube video. I have doses both tanks multiple times with H2O2 this way to control hair algae and not lost a single shrimp. It was ineffective against hydra though, unless I spot dosed directly on them which I did for a week or two before coming to the conclusion it was impossible to get rid of them all this way with the limited H2O2 available per dose.

Instead, I got some "No Planaria" and this worked within an hour or two to eliminate all hydra, whilst being completely safe for all shrimp and fish (it also was fine with my Malaysian Trumpet snails, but others have reported deaths with other snail types so probably best to remove).

My advise - H2O2 is not effective of eliminating hydra from a shrimp tank, but "No Planaria" works incredibly well. Full details in the thread linked above anyway.
@dinokath: I am suprised that H2O2 killed your hydra and shrimp. I think you must have either been dosing way higher than the 1.5ml per 4.5 litres I used, or there was something else in the H2O2 you used that was the active ingredient.
@faywayway: Get yourself some "No Planaria"!

Happy shrimpkeeping =)
James


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## Tiger15 (Jan 7, 2018)

en7jos said:


> My advise - H2O2 is not effective of eliminating hydra from a shrimp tank, but "No Planaria" works incredibly well. Full details in the thread linked above anyway.
> 
> @dinokath: I am suprised that H2O2 killed your hydra and shrimp. I think you must have either been dosing way higher than the 1.5ml per 4.5 litres I used, or there was something else in the H2O2 you used that was the active ingredient.
> 
> s


I am curious what exactly killed the OP shrimp so we can learn not to repeat.

I use H2O2 to regularly clean my 75g planted tank. I spray 3% H2O2 on all exposed plants and surfaces when I drained my 75g in WC. I never measured the quantity I use, but since I often finished up one 8 oz spray bottle per treatment, my estimated final dosage is about 2 ml per gal, and the initial dosage as much as 3 times higher or 6 ml per gal as the tank is slowly filled up. . Bear in mind that H2O2 is volatile and the agitation filling up the tank will break up most of it. I observe heavy bubbling for hours so there is residual dosage working, though much lower than the estimated amounts. The treatment is very effective in eliminating BBA and other algae, and do no harm to fish and nerite snails, but I have no shrimp in it

I’m not sure what it meant by food grade H2O2 as I’m not aware that H2O2 is used as a food additive. I use the pharmaceutical type on left of the picture that contains pure 3% H2O2. I also have the household cleaner H2O2 as shown on the right which should never be used in aquarium as it contains other unknown ingredients. 

1.5 ml 3% H2O2 per 4.5 liter is 1.5 ml per imperial gal that is equivalent to 1.2 ml per US gal. I’m planning to dose H2O2 to my shrimp bowl to combat hair algae, and want to make sure the dosage is right as there is no margin of error in a small bowl with no filter.

I still think that persistent use of peroxide will eventually eliminate hydra, but don’t count on one time magic.


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## en7jos (Jun 7, 2020)

Tiger15 said:


> I’m not sure what it meant by food grade H2O2 as I’m not aware that H2O2 is used as a food additive. I use the pharmaceutical type on left of the picture that contains pure 3% H2O2.


Same here, I have no idea what "food grade" means and I also use pharmaceutical grade from the local chemist. Guess the important thing is that it is "pure" without any sort of extras that could be harmful to the tank. Lot's of people seem to reiterate that is has to be "food grade", but I've not seen anyone explain what the difference is or what nasty additives to look out for.



Tiger15 said:


> 1.5 ml 3% H2O2 per 4.5 liter is 1.5 ml per imperial gal that is equivalent to 1.2 ml per US gal. I’m planning to dose H2O2 to my shrimp bowl to combat hair algae, and want to make sure the dosage is right as there is no margin of error in a small bowl with no filter.


Yes, and no. The dose which I know to be safe (as per Mark's Shrimp Tanks Youtube video and personal experience) is 1.5ml of 3% H2O2 per 4.5 litres of tank water.
So that's 1.5 / 4.5 = 0.33ml per litre
US gallon in 3.8 litres (right?), so 0.33 x 3.8 = 1.27 ml of 3% H2O2 per US gallon.

Mark's Shrimp Tanks mentioned that he noticed odd behavior in shrimp at 2ml per 4.5 litres, hence he backed off dosing to 1.5ml per 4.5 litres. Note that he didn't say it harmed shrimp at all at 2ml dose, just that shrimp started acting odd, so I assume that 2ml per 4.5 litres is at the limit of a "safe" (not harmful) dose - just to give some idea of what margins you are working within. Remember to take into account substrate, rocks, etc that subtract from true water volume of tank, otherwise you could be over-dosing.

My Malaysian trumpet snails have been fine at this dose, but someone posted that a nerite that was sat on top of bubbling substrate (i.e. high local dose) perished. So make sure you mix well with tank water and move any critters that seem to be sat on top of bubbles as a precaution.



Tiger15 said:


> I still think that persistent use of peroxide will eventually eliminate hydra, but don’t count on one time magic.


I honestly do not think that you can eliminate hydra from a tank using H2O2. I tried daily dosing of my small (10 litre) shrimp tank for two weeks, spot dosing where I could see hydra and some days going a bit over the recommended dosing. Those hydra that were directly squirted perished, but those in other areas of the tank were unaffected. The 1.5ml / 4.5 litre dose is not enough to kill hydra. I found that diluting 3% H2O2 50/50 with tank water in the syringe I was using to squirt it at hydra (giving in effect ~1.5% H2O2) was still effective for spot dosing, but much more dilution (let's say 1 part H2O2 to 2 parts tank water) made it ineffective.

The "whole tank" dose necessary to eliminate hydra would also harm shrimp, snails and beneficial bacteria. It is impossible to spot dose more than a small area of a tank whilst keeping within the 1.5ml / 4.5 litre rule, so why you kill those hydra you squirt, the rest of the tank are unaffected.

If you're looking to eliminate hydra, then I'm afraid H2O2 is not the solution. Believe me, I tried and tried since it was the only thing available to me during lock down! Get some "No Planaria" and job done!


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## Tiger15 (Jan 7, 2018)

en7jos said:


> If you're looking to eliminate hydra, then I'm afraid H2O2 is not the solution. Believe me, I tried and tried since it was the only thing available to me during lock down! Get some "No Planaria" and job done!


I guess you’re right. There may not be a safe Whole tank dosage to shrimp that is adequate to kill hydra. Only spot spraying 3% H2O2 directly to hydra kill them. The op must use very high dosage as he reported seeing hydra floating left and right after treatment, no wonder his shrimp were dead too but he didn’t mention it until months later. 

One difficulty dosing H2O2 for whole tank treatment is to maintain uniform concentration over time and space. H2O2 is volatile and differential turbulence in the tank water can render one area more concentrated than another, and the half life of H2O2 in water is short, probably no more than a few hours depending on turbulence.

Excel dosing is more reliable in maintaining uniform concentration for as long as a day given the half life of H2O2 is 10 hours. Has any one tried excel to treat hydra or algae in shrimp tanks. According to Seachem, excel is safe to shrimp following the recommended dosage.


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## Tiger15 (Jan 7, 2018)

en7jos said:


> If you're looking to eliminate hydra, then I'm afraid H2O2 is not the solution. Believe me, I tried and tried since it was the only thing available to me during lock down! Get some "No Planaria" and job done!


I guess you’re right. There may not be a safe whole tank dosage to shrimp that is adequate to kill hydra. Only spot spraying 3% H2O2 directly to hydra kill them. The op must use very high dosage as he reported seeing hydra floating left and right after treatment, no wonder his shrimp were dead too but he didn’t mention it until months later. 

One difficulty dosing H2O2 for whole tank treatment is to maintain uniform concentration over time and space. H2O2 is volatile and differential turbulence in the tank water can render one area more concentrated than another, and the half life of H2O2 in water is short, probably no more than couple hours depending on turbulence and light intensity.

Excel is an alternative and dosing is more reliable in maintaining uniform concentration for as Glut is only slightly volatile and the half life is 10 hours, meaning the dosage concentration is sustainable for many hours. Has any one tried excel to treat hydra or algae in shrimp tanks. I haven’t but according to Seachem, excel is safe to shrimp following the recommended dosage.


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## en7jos (Jun 7, 2020)

Morning @Tiger15,

I also tried Excel for getting rid of my hydra (like I said, I had limited options during lockdown so had to try what I had to hand!). My conclusion is that it doesn't work, again because at the levels at which it is toxic to hydra then it also becomes less safe for shrimp.

I know Seachem says Excel is "shrimp safe" but there are lots of threads on here about what this means. I don't think anyone has had immediate shrimp deaths after correctly dosing Excel, but the general opinion seems to be that shrimp do better without it, at least in terms of regular (daily) dosing.

Spot dosing of undiluted Excel does seem to instantly melt hydra. They shrivel up to a dot and drop from the glass within minutes. However whole tank dosing at the Seachem recommended dosing (big dose on day one, and smaller dose on the other 6 days of the week) is not strong enough to kill hydra in my experience. I have a planted tank where I was dosing Excel at the full dose for a month or two and which still have hydra. Not many, so maybe the Excel was limiting them, but definitely a small and thriving group of them in one corner of the tank.

As with H2O2, it seems the dose that would be necessary to kill hydra would also be sufficient to harm shrimp, especially the more sensitive ones.

Honestly, if you have hydra in a shrimp tank and want rid of them, you need either fenbendazole canine dewormer, or the "No Planaria" that I used. There are no other options that actually work and that aren't going to do more harm to your tank and shrimp!


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## Tiger15 (Jan 7, 2018)

en7jos said:


> Morning @Tiger15,
> 
> I have a planted tank where I was dosing Excel at the full dose for a month or two and which still have hydra. Not many, so maybe the Excel was limiting them, but definitely a small and thriving group of them in one corner of the tank.
> mp!


You demonstrated that excel and H2O2 are both shrimp safe following recommended dosage, just not enough to wipe out hydra.

Shrimp safe means no immediate death, and does not mean harmless. Shrimp can be harmed by not reproducing, or shortening their already short life. Long term use of any chemicals can potentially harm shrimp. I know professional shrimp breeders don’t even trust tap water, and rather use recomposed RO to take uncertainties out of tap.


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## en7jos (Jun 7, 2020)

Exactly! That's what I'm saying!

Neither H2O2 or Excel can be used to eliminate hydra from a shrimp aquarium as:
a) the "shrimp safe" doses do not kill hydra
b) long term dosing at the recommended "safe" dose is possibly / probably / definitely (depending upon who you ask) harmful in some way to shrimp (and still probably won't kill hydra), and
c) doses high enough to kill hydra will almost certainly harm shrimp (and other livestock and bacteria etc) too

Oh and the tank I dosed for several months with Excel only has amano shrimp who are quite hardy and don't successfully reproduce anyway. I wouldn't want to do the same in my CRS shrimp tank...

Hence only options are fenbendazole or No Planaria.


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