# Aeration in HoB filter?



## HamToast (May 6, 2012)

Would an effective alternative to using an air-stone in the tank be to put an air-stone in the reservoir of my HoB filter? I'm just curious since I don't care much for the wall of giant bubbles in my tank. They also splash onto my lights and I don't like cleaning the lights daily.

My reasoning behind this being a good alternative is that although surface tension in the tank won't be broken as much as without the bubbles, the surface in the reservoir would be much more agitated and so would be able to highly oxygenate the water in the filter. This would allow the water returning to the tank to be oxygenated already.

If that logic is correct then I'll go ahead and put two or three air-stones in my filter reservoir tomorrow when I do a PWC. If not, then I guess I'll have to find another option to replace the stones in the tank.


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## Django (Jun 13, 2012)

HamToast said:


> Would an effective alternative to using an air-stone in the tank be to put an air-stone in the reservoir of my HoB filter? I'm just curious since I don't care much for the wall of giant bubbles in my tank. They also splash onto my lights and I don't like cleaning the lights daily.
> 
> My reasoning behind this being a good alternative is that although surface tension in the tank won't be broken as much as without the bubbles, the surface in the reservoir would be much more agitated and so would be able to highly oxygenate the water in the filter. This would allow the water returning to the tank to be oxygenated already.
> 
> If that logic is correct then I'll go ahead and put two or three air-stones in my filter reservoir tomorrow when I do a PWC. If not, then I guess I'll have to find another option to replace the stones in the tank.


Hi! Good thinking, except do you need aeration? You get some from your HOB anyway. I have a 10-gallon tank with a HOB and I'm not getting any symptoms of lack of oxygen. Is this a planted tank? If you find that aeration is necessary, I don't see a problem with one airstone in the HOB. I don't know that more than one airstone would work in there, and there's also a limit to how much aeration can occur in such a small amount of water in the HOB.


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## HamToast (May 6, 2012)

Django said:


> Hi! Good thinking, except do you need aeration? You get some from your HOB anyway. I have a 10-gallon tank with a HOB and I'm not getting any symptoms of lack of oxygen. Is this a planted tank? If you find that aeration is necessary, I don't see a problem with one airstone in the HOB. I don't know that more than one airstone would work in there, and there's also a limit to how much aeration can occur in such a small amount of water in the HOB.


I didn't really consider the limits, but you're right. One or two air-stones would probably be about the limit, though I could fit a few more (all of them would have to be 6" or less). It has a pretty sizable reservoir for an HoB.

As for the other points you brought up: yes, it is a planted tank and unfortunately yes, I am having fish show symptoms of a lack of oxygen. I'm not entirely sure why, but I have been noticing them hang around the surface and gasping lately. All the water parameters are fine so the only other thing I can think of is that I could use some more aeration.


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## Django (Jun 13, 2012)

Some people consider water movement to be similar to aeration, but you should watch the plants and see if they're moving all over the tank. That brings oxygen from the surface to other places in the tank. Although I don't know how much adjusting you can do with a HOB - maybe move it and check again. I don't see as much water movement at the other end of my tank, but they say for slow-water fish, put the HOB on the back, otherwise go from end to end. Hope things work out well for you.


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## Django (Jun 13, 2012)

Er, one more thing, it's been hot around here lately, probably heating up tanks. As the tank heat rises, in case you don't already know, it is less able to carry dissolved oxygen.

I hate to say the O word, but just to cover all the bases, I think overstocking sometimes contributes to low oxygen because it increases the bioload and the biofilter increases along with its oxygen usage, not to mention the fishes' oxygen use.


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## pejerrey (Dec 5, 2011)

I think I link this thread a couple of times a day, it's about why we're suffocating out bugs:

http://www.barrreport.com/showthread.php?t=10282

Please read.

I think you can improve the oxygenation greatly by increasing the surface agitation until you create a nice ripple without splashing thus no surface scum either.


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## HD Blazingwolf (May 12, 2011)

pejerrey said:


> I think I link this thread a couple of times a day, it's about why we're suffocating out bugs:
> 
> http://www.barrreport.com/showthread.php?t=10282
> 
> ...


 
it is a good thread to link for many a people. it would probably be easier to just pos tom's statements as a whole

but to clarify. surface ripple will not always handle surface film. the type of film will determine that. whether its a protein or bacterial film. a fungus? is it an oil residue from house cleaning products or candles?? these will all play a factor


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## pejerrey (Dec 5, 2011)

HD Blazingwolf said:


> it is a good thread to link for many a people. it would probably be easier to just pos tom's statements as a whole
> 
> but to clarify. surface ripple will not always handle surface film. the type of film will determine that. whether its a protein or bacterial film. a fungus? is it an oil residue from house cleaning products or candles?? these will all play a factor


Or is it chevron's fault? 

The link is better in this case because there is a good conversation where good questions are answered.


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## 50089 (Dec 11, 2011)

There are small air stones, not just the large bubble walls. You could stick a small one in the opposite corner of the HOB so you'd hardly see it and it might help the fish. If they're gasping at the surface that's an issue. An air stone in the HOB is an idea but I'd worry that some air bubbles could get sucked back up into the intake.


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## Kathyy (Feb 22, 2010)

Putting an airstone in the filter may do a great job of oxygenating the water but if that water doesn't circulate throughout the tank there are likely to be spots with low oxygen in the tank itself anyway. I would put that airstone in a spot where you see no water movement. Perhaps drop a pinch of fish food in the tank to see where it floats to the bottom or where the food doesn't go?

I look for a ripple on the surface of my tank to oxygenate the water but unless there is water flow throughout the tank any fish or plants in the stagnant places may suffer.

My platies aren't happy at the moment, some of them hang around the surface more than happy platies do. For a while I was cutting back on the amount of dechlor I was using. When I went back to the suggested dosage they are act more normally. Sometimes water companies change the water treatment without notice. You might check to see if yours has increased or changed treatment.


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## HamToast (May 6, 2012)

I do need more water flow in the tank, I already know that for sure. A friend of mine from my home town will be visiting next week and is bringing something that should help with that (he was unclear as to if it is a small power head or pump or what, so I am not totally sure). According to him, it also helps to oxygenate the water a bit. A smaller air-stone would be better than the wand/wall type, but I have still gotten lots of splashing onto my lights using those smaller ones.

Kathyy, my water company very well may have changed something up on me. I've noticed over the last month that the pH in the tank is lower than it normally is after a PWC. I tested the tap water, and the pH from the tap has dropped from 8.0 to almost 7.0. The tank pH has been slightly acidic since then as a result, but this is in comparison to it usually being about 7.5. I would suspect that the company may have also changed some of the other properties of the water.

My game plan now is to add the air-stone to the filter reservoir and monitor the fish closely to note any changes in behavior, good or bad. I'll also add the water flow fix that my friend is bringing and see if that helps as well. I should probably also look into having the water company send me an updated water table.


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## WestHaven (Jun 30, 2012)

HamToast said:


> Kathyy, my water company very well may have changed something up on me. I've noticed over the last month that the pH in the tank is lower than it normally is after a PWC. I tested the tap water, and the pH from the tap has dropped from 8.0 to almost 7.0. The tank pH has been slightly acidic since then as a result, but this is in comparison to it usually being about 7.5. I would suspect that the company may have also changed some of the other properties of the water.
> 
> My game plan now is to add the air-stone to the filter reservoir and monitor the fish closely to note any changes in behavior, good or bad. I'll also add the water flow fix that my friend is bringing and see if that helps as well. I should probably also look into having the water company send me an updated water table.


That's a good idea. Most cities/counties are more than happy to send citizens a detailed report on their water sources and decontamination. When I was living in Detroit a few years ago, the city/county water authority would send a report to everyone in the city once a year.


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## pejerrey (Dec 5, 2011)

As far as I know, the diluted oxygen that an airstone adds is not from the bubbles. You are not injecting pure o2 as when you do with co2. The surface agitation the airstone bubbles make is what helps. I may be wrong tho, or partially wrong.

Anyone want to chime in about that? Thanks.

However, I'm very curious about this experiment. Please report any results.


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## pejerrey (Dec 5, 2011)

I found a good read about the topic of aeration. As I was saying using air you can't go further than the concentration of o2 in air. So there is a limit.

http://www.barrreport.com/showthread.php?t=9494


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## HamToast (May 6, 2012)

pejerrey said:


> As far as I know, the diluted oxygen that an airstone adds is not from the bubbles. You are not injecting pure o2 as when you do with co2. The surface agitation the airstone bubbles make is what helps. I may be wrong tho, or partially wrong.
> 
> Anyone want to chime in about that? Thanks.
> 
> However, I'm very curious about this experiment. Please report any results.


From what I have read, it works based on breaking surface tension and causing transfer of gasses. By making bubbles, there is a secondary effect as each bubble makes contact with the water and creates its own tiny surface tension within the water. The secondary action, while not as effective as breaking the surface tension, can also add to the gas transfer. So like you said, it is not injecting O2 into the water as a CO2 setup would do.

I wish I had some way of measuring exactly how much O2 is in the water. The best I could do is a drop checker and make sure there isn't too much CO2, then just use my best guess to determine of the O2 levels are appropriate. Not very accurate but it could give a general idea of if this is working or not.


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## Diana (Jan 14, 2010)

Run an air pump with a good bubbler in the tank when you are not there. Run it on a timer.
I used bubblers in the summer when the tanks would warm up. It was just enough to keep the oxygen just that little bit higher. 
My tanks are less stocked now, and better conditions for the plants, so I have not used the air pumps for a couple of years.


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## HamToast (May 6, 2012)

Diana said:


> Run an air pump with a good bubbler in the tank when you are not there. Run it on a timer.
> I used bubblers in the summer when the tanks would warm up. It was just enough to keep the oxygen just that little bit higher.
> My tanks are less stocked now, and better conditions for the plants, so I have not used the air pumps for a couple of years.


Yep, this would work, but it'd still splash my lights.

I'm just experimenting to find a functioning alternative to the typical air-stone in the tank.


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## HamToast (May 6, 2012)

So far there hasn't been any improvement. It looks like I'll need to add an air-stone to the inside of the tank like I had before and just deal with the splashing. At least until I get something better to aerate the tank with.


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## Diana (Jan 14, 2010)

Oh, sorry. 

Put a fountain pump on the bottom middle of the tank. Aim the outlet vertically. 
If you select the right pump you will get some pretty good surface movement without any splashing. Protect the intake so substrate and leaves do not block it. 
This sort of set up is called a flume. 

This is the best way to get the bottom water circulated to the top for gas exchange. Probably more efficient in terms of electricity, too.


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## HamToast (May 6, 2012)

Diana said:


> Oh, sorry.
> 
> Put a fountain pump on the bottom middle of the tank. Aim the outlet vertically.
> If you select the right pump you will get some pretty good surface movement without any splashing. Protect the intake so substrate and leaves do not block it.
> ...


I'll look into this ASAP! Thanks. I had not heard of this before.


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## Stormtrooper (Aug 28, 2012)

Hi I'm new and a just set up a new 20 gallon tank. I had a aquarium for a few years and I never did much research untill now when we resetup the tank. Iv learned alot of stuff I didn't know before. Anyway the tank had a hob filter but it was in a bedroom do the water was filled all the way up so no noise. After research I realized my fish probably wouldn't be getting enough oxygen. The hob wasn't splashing or making bubbles and the house is on the warm side so the temp will not drop below 80-81. I never really like bubble walls so I wanted a more hidden way to add oxygen. I had the idea to add airstones to the hob filter and soon after trying to research if that had been done before I found this site. Anyway I went and got a whisper 30-60 gallon air pump so I had plenty of air for anything I wanted.







I ran one outlet on the pump into a distribution block thingy then had a seperates line going into each hob filter with both having adjustment knobs. Even though my filter was rated for a 20 gallon I didn't think it was moving enough water so I added another one to the other side. I have the air stones really low to keep quiet and the seem to do the job great. There were no bubbles at all coming from the hobs now there's alot. If you didn't care about noise you can really churn up the water in the hob. I have the airstones after the filters the bubbles come up the down the water fall spreading out through top of the tank. it's hard to see in the pic because the bubble move to fast but going from none at all to that looks like it makes a big difference. Unfortunately the girlfriend wanted a bubble wall anyway so now I have both. Turned out nice though. Id say it's a good alternative to having air stones in the tank if you don't like them.







this picture is kind blurry but it shows the setup. the bubbles coming from the castle are cool though I just plumbed tubing through the castle and the fish seem to enjoy it.

I don't know If my pics are gonna work but if not hopefully I described it enough


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## HamToast (May 6, 2012)

I have been running just about the exact setup as you, Stormtrooper, with an air-stone in each filter. The main difference is just that my HoB has two sections (one on each side of the impeller) so I have a stone in each section. Running it just like that did not add any bubbles to the tank for me though. I'm not really sure why.

For about a week I noticed slight but steady improvement in fish health and behavior. I feel that adding the stones did a good job in helping to aerate the water over time. I added a water pump to increase current flow and surface agitation and since doing this, the stones and pump combined seem to really make the fish quite happy. Cherry barbs have spawned some eggs, and all of the fish are active and playful.

Also, welcome to plantedtank.net!


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## Diana (Jan 14, 2010)

Air bubbles from most bubblers rise to the surface and pop, not adding any significant air to the water. 

Rising air bubbles from the bottom of the aquarium also create a rising column of water. This water from lower in the tank spreads out across the surface of the tank. When the water from the bottom is in contact with the air, gas exchange happens. In the tank in the picture, for example, the water at the bottom of the tank is high in CO2, low in oxygen. (not enough live plants). When this water gets to the top it loses most of the CO2 and gains oxygen. More rising water takes its place, and the oxygen enriched water finds it way back down into the lower parts of the tank. 

Water circulation does not have to come from a bubbler. Most filters are set up to do this already: Pick up water from lower in the tank and spread it across the surface. 
Yes, most HOB (Hang On Back) filters are over rated. Look at the gallons per hour and buy a large enough filter that it will circulate the aquarium water 10 times per hour. So, a 20 gallon tank needs a filter capable of 200 gph. 
Power heads do a similar job: The intake is fairly low, the outlet is usually set up near the surface, again, creating that bottom-to-top circulation. 

The more direct method is often used in ponds and enclosed lakes. 
A large pump near the bottom picks up water and sends it across the surface of the pond. It can splash the water like a fountain, and this can help, but it is the bottom-to-top circulation that is doing most of the work. This is the set up I suggested above, where the splashing was not wanted.


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## HamToast (May 6, 2012)

Diana said:


> Air bubbles from most bubblers rise to the surface and pop, not adding any significant air to the water.
> 
> Rising air bubbles from the bottom of the aquarium also create a rising column of water. This water from lower in the tank spreads out across the surface of the tank. When the water from the bottom is in contact with the air, gas exchange happens. In the tank in the picture, for example, the water at the bottom of the tank is high in CO2, low in oxygen. (not enough live plants). When this water gets to the top it loses most of the CO2 and gains oxygen. More rising water takes its place, and the oxygen enriched water finds it way back down into the lower parts of the tank.
> 
> ...


I ended up using a filter/pump my friend gave me and experimented over the course of this week to find a good angle to aim the outlet. It seems to circulate the water fairly well and the fish seem to be enjoying the tank wonderfully.

As for the bubbles in the HoB: while the bubbles will not cause any increased circulation throughout the tank as they are intended to do under their recommended operation, they should still provide a greatly increased amount of surface agitation within the filter reservoir. Although the amount of space is limited when compared to the entire tank, the highly increased surface agitation within the reservoir should benefit the amount of gas transfer that will take place on the top of the water. In turn, this should allow for a slight but noticeable increase in overall oxygenation in the tank. I have been able to observe this take place, although I admit I have no means to actually measure the levels of oxygen in the water. I am using observations of fish behavior before and after the bubbles in the filter as a guide. When I combine the moderate benefits of the bubbles in the HoB filter with a decent current from a pump, I seem to get a fairly good result.

I will run the tank as it is for a few weeks and carefully observe the fish behavior as well as the tank's general health (plants, water parameters, etc.). After I feel the tank is fully stable and has not progressed or regressed in a week or two, I will rearrange the filter/pump to the setup you recommended, Diana. I'm curious to compare the method you recommended with the method I have running currently and observe the effect a vertical current would have on the behavior of the tank's inhabitants.

Right now, I have stabilized the health of the tank's inhabitants and am at a dead end with what I can do with my tank (further aquascaping and increased stocking are ill advisable for the time being), so I am going to do a bit of experimenting with different circulation methods. I'm excited to note and report the results and am very pleased to have been given a specific method to try (thanks Diana!).


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## Diana (Jan 14, 2010)

Indeed, the circulation is the key. 
Water in contact with the air needs to be circulated down, and the water from lower down needs to be exposed to the air in a constant cycle. 

There are all sorts of tools to do this, and as you are doing: Test different locations and see the results. It is interesting that the little bit of added aeration inside the filter is enough to see a difference in the tank. I would have thought:
a) Water in the filter is already churning pretty well, how much more can it be agitated?
b) Once the water leaves the filter it sheets across the surface, so it could just as easily pick up oxygen there, so adjusting it so it sheets the best is easier than running a bubbler in the filter. 
Yet, you are seeing improved fish behavior, suggesting better aeration. Interesting... 

Remember that warmer water holds less oxygen, so if some of your tests happen when the tank is warmer than average, make sure to repeat those tests when the tank cools back down to be able to properly compare the results.


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## HamToast (May 6, 2012)

Diana said:


> Indeed, the circulation is the key.
> Water in contact with the air needs to be circulated down, and the water from lower down needs to be exposed to the air in a constant cycle.
> 
> There are all sorts of tools to do this, and as you are doing: Test different locations and see the results. It is interesting that the little bit of added aeration inside the filter is enough to see a difference in the tank. I would have thought:
> ...


I didn't think about temperature, but its entirely possible that the temperature of the tank effected my fish and led me to believe a false result. The week or two before adding the air-stones in the HoB were very hot, and when I added the air-stones the weather became very rainy and cooled down significantly. The ambient house temperature always varies based on the outside temperature, and so does the tank's temperature. I may run another trial with just the air-stones and see if the fish behave the same as they did before since the weather is hot again.


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