Tight Fitting Tank Covers

[newfishaddict]

I have planted tanks with DIY co2 and I have successfully used Zigs EI to maintain algae free tanks.

My tanks are tightly covered with glass Marineland covers. There are a few small spaces in the glass (and plastic) covers where airline/co2lines run into the tank but these are the only holes in the cover.

I am wondering: wouldn’t a tank with no top on it have much higher dissolved oxygen in the water? I am concerned that my tight fitting top (that does trap in most evaporating water from the tank) be tight enough that the oxygen transfer from the atmosphere is being limited.

I am just thinking that if a tank has a tight fitting top and no air-stone (the pump being a source of air from outside the tank) that the tank has limited access to oxygen from the air…

I surmise that I should have numerous small holes in the plastic part of my glass tank covers to facilitate oxygen transfer into the tank’s water, is this recommended?

 

[ncjharris]

Interesting theory (plus I like any conversation that mentions tight fitting tops, but thats neither here nor there)

However, I would have thought (and at the moment I have nothing to back this up other than what remains of my 'a' level phyics) that no.

Considering Oxygen is something like 20% of the composition of air, I would have thought there would always be some gas exchanged due to the comparative amounts of o2 in the air and the water.
Considering that the amount of oxygen contained in the water is largely temperature dependent, this transfer would occur while the air is exchanged between inside the hood and outside.
As nature abhours a vacuum, where there is a lower density of oxygen, the higher density (as a proportion) will fill in where the transfer has taken place.
In the same way that if you are in a small room, so long as it is not completley air tight, you won't suffocate. Perhaps.

I have just reread this and it makes no sence. I'm going to post it in the hope someone takes pity and supplies the correct answer.

 

[newfishaddict]

I understand what you are getting at, and becuase my fish are fine, to some degree there must be enough o2 getting into my water however, I am reasonably certain that the o2 level in the tank will go up with a tank cover that is not as tight fitting.....I am wondering if someone knows the facts on this....

I suspect the inch or two of air, between the water surface and and glass top, has a lower o2 content than the air in my room, I am trying to find out how much this difference is....

 

[Opcn]

I never had a problem with my nanocube