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CO2 concentration and aquariums with lids

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5.5K views 2 replies 3 participants last post by  exv152  
#1 ·
Recently I learned that an external canister filter can easily increase aquarium temperature by 2 degrees all by itself. My ambient temp was at 22.5 C and I noticed it climb to 24.5C a few days after WC. Apparently having a lid on in combination with the canister filter was enough.

So I made a test - what would happen if I left the lid open for 2 days? As you'd expect, tank temperature dropped to ambient 22.5C. However now I noticed that my CO2 concentration seems lower too, with the same exact BPS.

Can a lid (plastic one, with quite substantial seams and holes) keep CO2 in so well, that having it closed increases CO2 rate in the tank? CO2 is injected with an inline diffuser.

I noticed that my pH degassed was higher than I had measured earlier, and also when lights got on (so CO2 had been on for 1.5h without lights) my pH had not dropped nearly as much as it normally would. Now seems that CO2 is rising much slower than before.
 
S
#2 ·
Interesting. I just three days ago took out the glass from my lid that was under the light. Therefore opening a large portion of my lid. I've noticed no change in readings from my ph probe/controller. I don't watch my flowrwte or bps as the controller does that for me. And I prefer it to run heavy enough that it cycles off so that I get viewing time with the tank clear as I run a inline diffuser as well on a canister filter. I do have a dropchecker in the tank as a reference and have not noticed any change in it either.
 
#3 ·
CO2 and O2 are affected by air flow at the water surface. If you use a lid, I would not be surprised to see that CO2 off gassing is slowed down. That said, an open top is preferable with planted tanks so you get that full off gassing over night, which helps the tank replenish it’s O2 concentration for the fish. Unless you have jumpers in the tank, I prefer to go open top.
 
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