# how to revive fish after CO2 overdose



## Planteater (Aug 6, 2009)

my solenoid malfunctioned and i found all the fish on the surface, still alive.

eventually about half died, all siamese algae eaters, some otos, corys, and lots of tetra. my discus seem to be making a comeback but one is super shy and not flying straight.

is there anything i can do to help them, since it seems it takes some time for them to die. i did massive water change, a good dose of light for the photosynthesis, and the last thing i did was add a little H202. No one has died since but i was wondering if there is anything one can do.

it seems to me that relying on a solenoid is like playing russian roulette. even if I get a new one, it could just happen again. maybe i will go away for a few days sometime and find them all dead.

do you guys worry about your solenoid at all? based on my experience, you should.

Planteater


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## Darkblade48 (Jan 4, 2008)

Sorry to hear about your losses. 

Water changes are good, but I don't really see the point of increasing light for photosynthesis...

Adding the peroxide was probably a mistake. CO2 does not displace oxygen from the water, so there really isn't a need to add H2O2. The best thing that you can do is to put in an airstone and have an airpump going so that the CO2 diffuses into the atmosphere. Other methods of surface turbulence (i.e. raising a canister spray bar, etc) will also help get rid of excess CO2 in your water.

If you get a reliable solenoid, and you install it properly (i.e. do not use teflon tape, but use a non-hardening pipe compound), you should not need to worry about a solenoid not closing.


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## Hoppy (Dec 24, 2005)

I'm assuming you use a pH controller to control the solenoid? If you don't, and you set the bubble rate right, plus have good water surface ripple, you shouldn't be in too much trouble even if the solenoid fails. The concentration of CO2 might go up a bit more than you prefer at night, but hopefully not enough to kill the fish. Like most CO2 components, it pays in the long haul to buy good quality not low price.


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## BottomFeeder (Jul 26, 2008)

Sorry to hear about the troubles. I have bunch of air pumps that I use for sponges in other tanks. I always have one handy if I see the fish under stress.


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## jaidexl (Sep 18, 2006)

I've saved my fish from it two or three times, one time a bulldog pleco was laying upside down on a stand of stargrass, gasping for an hour. I used the same process every time.

Removed a third of the water (as low as the filter will allow) to lower the surface for more splashing from the filter outlet, and to reduce the volume of water I'm dealing with (speed the process of degassing). 

Did 10 to 15% water changes over and over, maybe 3 or 4 in a row. Dumped water in to create as much surface disruption as possible. 

Ran airpump with open ended hose, the larger bubbles rise faster and create the most agitation you can get from an airpump, versus using a stone.

Sat on the couch and chewed off my nails.

Worked every time roud:

Tips from my experiences... never use a Clippard needle valve, and never underestimate the efficiency of a limewood diffuser under a canister outlet that is pointing down.


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## Planteater (Aug 6, 2009)

i did pay big bucks for my regulator, which i bought pre-assembled with solenoid. so even if I get it exchanged, how do i know the next one wont fail? There is no warning.

one more tetra dead this morning. i guess the worst is over. a couple of the otos hang out near the surface where they never did before, perhaps their gills are not working so well, but they seem otherwise fine.

do you know if the fish have been permanently damaged and if there is anything i can do?


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## captain_bu (Oct 20, 2007)

Planteater said:


> i did pay big bucks for my regulator, which i bought pre-assembled with solenoid. so even if I get it exchanged, how do i know the next one wont fail? There is no warning.


You don't know that a solenoid won't fail... it is the one part of a manual regulator that is prone to fail since it is electronic, a good quality needle valve and regulator body should last pretty near forever if you don't drop or otherwise impact it. Solenoids can and will wear out. Best to make sure the tank has either an air pump running or enough surface agitation at night to prevent gassing your fish if the solenoid or timer should fail. The more oxygen your fish have available to them while the CO2 is off the more tolerance they will have for daytime CO2 levels.


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## Planteater (Aug 6, 2009)

i had the regulator and solenoid in service for only one week. so thats what i mean by the solenoid being a huge gamble. if it can fail after one week, what about two months, two years, tomorrow or the next day? What about any time?

thanks for the advice about surface agitation at night. but if i am adjusting the turbulence at night then why not just turn the gas off manually? and if the turbulence is on all the time to reduce c02, doesnt that defeat the purpose of the expensive co2 system?

thanks for clearing up any confusion i might have...

Planteater


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## Darkblade48 (Jan 4, 2008)

Planteater said:


> i had the regulator and solenoid in service for only one week. so thats what i mean by the solenoid being a huge gamble. if it can fail after one week, what about two months, two years, tomorrow or the next day? What about any time?


Perhaps you just got a bad solenoid to start off with. They usually are made well, but it is not impossible for them to fail.



Planteater said:


> thanks for the advice about surface agitation at night. but if i am adjusting the turbulence at night then why not just turn the gas off manually?


While you can do this, turning the CO2 tank on and off manually is a hassle, and you may forget to do it one day, etc.



Planteater said:


> and if the turbulence is on all the time to reduce c02, doesnt that defeat the purpose of the expensive co2 system?


You do not keep the turbulence (i.e. from an airstone) on all the time. Instead, you keep the CO2 on all the time, and simply have the turbulence come on at night (i.e. put the airpump on a timer).


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## jaidexl (Sep 18, 2006)

double post


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## jaidexl (Sep 18, 2006)

If it makes you feel any better, I've used three different solenoids extensively with no problems, all different brands. You're accident is pretty uncommon from my point of view, things I read from others etc, I'm sure there's a 100x better chance of algae destroying the tank. I would use the warranty if it's still in place. What brand is it?


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## captain_bu (Oct 20, 2007)

Planteater said:


> thanks for the advice about surface agitation at night. but if i am adjusting the turbulence at night then why not just turn the gas off manually? and if the turbulence is on all the time to reduce c02, doesnt that defeat the purpose of the expensive co2 system?


Agree that you probably got a defective solenoid but the point is that they are the one part of a CO2 rig that is most prone to failure.

As far as turning off the gas manually, this is fine if you are always home at night and never forget... much better chance that your solenoid will be more reliable than you are despite your experience with a defective solenoid. 

02 and CO2 levels in the tank coexist, having enough oxygen in the tank does not preclude having enough CO2, if you need X amount of surface agitation during the day to keep the O2 level high enough for the fish to thrive you simply turn up the CO2 to compensate.

If you only want to increase surface agitation at night connect an airstone or powerhead to a timer, there is no reason to have to turn on or off any equipment manually.


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## Rick1270 (Jun 1, 2017)

Just because I had an extra laying around... I put two solenoids on my system... probably overkill but the redundancy gives me a little extra peace of mind


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## Bettatail (Feb 12, 2009)

Rick1270 said:


> Just because I had an extra laying around... I put two solenoids on my system... probably overkill but the redundancy gives me a little extra peace of mind


I don't think you need two solenoids.

thread started in 2009, at the time, a lot of solenoids in aquarium co2 system were not intended for low flow, low power consumption and constantly hold application. 
many failed...

now it is 2019, a lot of experienced hobbyists know what solenoids to choose for their co2 system.


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## PlantedRich (Jul 21, 2010)

I suspect the problem is not that one is using a solenoid but that we are often sold solenoids which are not very good, even when we are paying a very high price for the set. It often requires looking at things and finding why they fail, rather than simply looking at the price. Solenoids which fail are most often due to the design and fall into what I call the "black box" group. 
Perhaps it is time to look at why these are so common and then why they fail so often. 
Inside the black box, we often find a small metal "pellet" which moves when the electromagnet is energized and then moves back by a spring. To make this seal, the space has to be really tight and that can be a real problem when we operate the solenoid for the long term we use like several hours. The current flow generates enough heat to dry any lube as well as slightly distort the shape of the pellet and reduce the spring force. A dry pellet that has swelled just a bit, will often not move when a spring is a bit weaker than when new! There is often also another small bit of metal which will click but that doesn't mean the flow stops when the real action doesn't happen. 
So I look for a far better solenoid and change out the el-cheapo that we often find provided, even with high priced sets. I go for the Clippard Mouse series for the extreme low current flow which cannot produce heat as well as the totally different interior mechanism.


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