# Sponge filter question



## abak (Nov 27, 2016)

Hi I was wondering if anyone can tell me if I'm doing more harm then good by having a sponge filter in my el natural 6-7 gal tank? I put it in there just for some circulation and a little bit of surface movement but I've been reading up on this forum and I have a feeling that it might not be a good idea with live plants? Does it suck up ammonia that the plants need by having that sponge in there? Should I just use an air stone for the water movement instead? Also if I remove it would it mess up the tank and make it cycle again since its housing beneficial bacteria? Sorry I know it's probably a rookie question but I'm barely into all this so have no idea.

Here is a picture of the tank. I only have 3 adult guppies and about 5 juveniles (that I will be rehoming soon) in there. Oh and three snails. I know a bit overstocked but it's working for now.


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## s2man (Nov 8, 2016)

Hi Abak. Yes, the sponge filter will remove, well, convert the ammonia and nitrites into nitrates, which are harder for the plants to take up. And the surface agitation will allow the CO2 to escape from the water to the air. I think Diana calls CO2 the most important plant nutrient. 

I have a small sponge filter in my large tank, but just to keep it baceriated (I just made up that word : -) so it is ready to move to the quarantine tank at any time. The bubbles from it were really agitating the surface so I put an airstone in it and had a much smoother water surface. And, I put a Tee and valve in the air line and reduced the air flow to a minimum. I think a small airstone should give you what you are looking for in circulation without agitation. 

I would think you will be fine removing the filter and relying on the plants. But I suggest you wait for a more experienced El Narural person's comments on your fish load. Diana just says to have a 'moderate' load. I don't know a rule for calculating moderate.  I used aqadvisor.com, using biological filters for input, and I plan to stock my tank at about 60% of their recommendation, fwiw. 

Nice looking tank. I like it.


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## Michael (Jul 20, 2010)

You aren't doing much harm with the sponge filter, but it probably is not necessary either. Your tank certainly is not overstocked and is heavily planted, so the plants can take care of any filtration needs. What would be helpful is some water circulation from a very small powerhead, hang on back filter, or an airstone set on low.


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## abak (Nov 27, 2016)

Thanks for the replies. I will remove the filter and put an air stone for circulation. Will probably clamp it to slow it down for desired affect. I sure appreciate all your help guys!

Im glad to know my tank isn't overstocked as one of the mama guppies is about ready to drop more fry. I'm still planning to give away the juveniles but at least I know the babies won't be too much for now. I do have a bigger tank on my wish list for my birthday next month . Then I can use the bigger tank for my favorite guppies and make this one a cherry shrimp breeding tank


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## mettadas (Oct 12, 2016)

s2man said:


> Hi Abak. Yes, the sponge filter will remove, well, convert the ammonia and nitrites into nitrates, which are harder for the plants to take up. And the surface agitation will allow the CO2 to escape from the water to the air. I think Diana calls CO2 the most important plant nutrient.


If you have been adding more CO2 to your tank than the air/water equalibirum point for your conditions, then yes, agitation will cost you some. This is the case for people bubbling CO2 into their high tech tanks. But if your water has less CO2 than the equalibirum point, for example because your plants have used some, then I would expect agitation to increase the rate at which CO2 enters the water from the air.


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## s2man (Nov 8, 2016)

Ah yes, mettadas, but we are talking about natural tanks where the decomposing organic matter is providing CO2 which builds up during the night and the siesta period. In a non-natural tank I would agree, yes, agitate that surface to keep the water CO2 in equalibrium with the atmosphere. Just as surface agitation is desirable in a non-planted tank to increase dissolve oxygen.


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## Z1234 (Oct 25, 2016)

s2man said:


> In a non-natural tank I would agree, yes, agitate that surface to keep the water CO2 in equalibrium with the atmosphere.


_Guys, I am no biologist nor chemist, so I might be completely wrong on this._

To my understanding, which of course might be totally wrong, water CO2-air equilibrium provides only ~0.5 mg / liter CO2 in water. This sounds terribly low to me compared to the levels that we saw on the example siesta CO2 level chart. I don't know how fast CO2 from air can dissolve in water, but that also might be a slow process? ... and as I understood, if water CO2 level is higher than ~0.5 mg/l, then CO2 will gas out to air. The more mixing, the faster.

So my guess is, if a low-tech non NPT planted tank relies on air CO2 alone as a C source, then plant growth might be very poor. Tap water can have alot of CO2/HCO3-, so frequent water changes might help? NPTs do not rely on that.

I'd guess that a large biofilter could also provide CO2 in a low tech non-NPT tank, as long as its not cleaned very frequently. Maybe I am wrong again.



s2man said:


> In a non-natural tank I would agree, yes, agitate that surface to keep the water CO2 in equalibrium with the atmosphere. Just as surface agitation is desirable in a non-planted tank to increase dissolve oxygen.


O2 is needed to fuel some bacterial processes, I'd guess if a tank runs out of O2, that's a disaster. However, I have never seen fish gasping for air in any of my NPTs, not even in the ones with no water movement at all. Plants grow reasonable OK in some of my tanks even in still water. Maybe these are not ideal conditions or maybe these tanks are on the edge? Or maybe I don't have a huge amount of fish? But I really check the fish in the mornings and I have never seen any sign of low O2 levels. They just seem to be happy.

Maybe this is also a bad practice, but sometimes I turn off watercirculation completely (no biofilter!) for 1-2-3 days to see if some small floating particles settle down. Water clarity is rarely a problem for me, but occasionally is.

I see more and more studies that (some) plants can take up CO2 directly from sediment. This is where NPTs also have an advantage?


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## dwalstad (Apr 14, 2006)

abak said:


> Hi I was wondering if anyone can tell me if I'm doing more harm then good by having a sponge filter in my el natural 6-7 gal tank? I put it in there just for some circulation and a little bit of surface movement but I've been reading up on this forum and I have a feeling that it might not be a good idea with live plants? Does it suck up ammonia that the plants need by having that sponge in there? Should I just use an air stone for the water movement instead? Also if I remove it would it mess up the tank and make it cycle again since its housing beneficial bacteria? Sorry I know it's probably a rookie question but I'm barely into all this so have no idea.
> 
> Here is a picture of the tank. I only have 3 adult guppies and about 5 juveniles (that I will be rehoming soon) in there. Oh and three snails. I know a bit overstocked but it's working for now.


What a lovely little tank! Since it is doing so well, I'm not sure I would change a thing.

(A little sponge filter like yours with gentle, slow air bubbling probably is not hurting the plants.)


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## Z1234 (Oct 25, 2016)

dwalstad said:


> What a lovely little tank! Since it is doing so well, I'm not sure I would change a thing.
> 
> (A little sponge filter like yours with gentle, slow air bubbling probably is not hurting the plants.)


I think this is the point. If the water flow is very strong, then the filter will likely collect much more "stuff", even larger particles will land in it. Then to prevent that the filter gets clogged, either more frequent cleaning is needed, or the filter size needs to be increased.

I used to have such a low-tech dirted planted aquarium with a huge external biological filter. My biggest fish kill happened when I was on holiday and the external filter stopped working. By the time I got home, all of my Hemigrammus bleheri was gone (10+). Other, less sensitive species did poorly, but survived. Since then I realized that my tanks can work fine without the huge external filter. (I don't recommend anyone reading this to run and unplug the external filter on their tanks. Once a tank already depends on it, probably a more steady / planed approach is needed)

Back to the sponge filter, I guess it cannot go severely anaerobic in case flow stops, and some flow is probably good to have in the tank. Plus it might help to get rid of some of the annoying floating particles. (if there is any...)

Surface scum can be an issue, but I guess that's another topic to discuss.


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## abak (Nov 27, 2016)

Thanks everyone for all the input! I appreciate you all. And no I don't supplement with co2.

Also I clean the filter once a month in the old aquarium water by gently squeezing and rinsing it and then it goes right back in.



dwalstad said:


> What a lovely little tank! Since it is doing so well, I'm not sure I would change a thing.
> 
> (A little sponge filter like yours with gentle, slow air bubbling probably is not hurting the plants.)


Thank you! I'm honored to have your input  I actually never removed the sponge filter like I wanted to. I just added some cherry shrimp in there yesterday and figured they would love to have that sponge as an extra food source. I have it turned down quite a bit so the flow is really slow. Just enough to send some tiny ripples through the surface.

Anyway all my creatures seem happy so I figure I will leave things the way they are


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## dwalstad (Apr 14, 2006)

You've got a good plan for this tank-- do nothing.
The shrimp will probably enjoy feeding off the protozoa that feed on the bacteria in the sponge filter.
Those algae balls are really cool!


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