how tightly can we cover our tanks, without effecting oxygenation???

[Magnum Man]

so, the bulk of my tanks are open topped, maybe 1/4 have a cover, but most are set up so terrestrial plants can grow out of them… but my 3 season porch tank, I want sealed tighter, to limit evaporation during the dry winter months… I would assume that if we are using an air pump, we will get oxygen from that, but I believe the bulk still comes from surface agitation… my outside tank currently has custom cut plate glass, that fit precisely into the recess in the frame, I do have the 2 back corners pretty tightly cut off so there is barely space between the frame and the glass for an air line, and a heater cord… without those cuts, the air pump would have to force air out under the glass to relieve the pressure, so that warrants the question of how tightly can we seal our tanks, with out dramatically reducing the ability to oxygenate the water???

 

[Rusty_Shackleford]

I believe there has to be some opening to let atmospheric oxygen into the aquarium. Surface agitation will help with the gaseous exchange, but where does that CO² go if your tanks is sealed tightly?
CO² is heavier than oxygen which means it will sit there just above the surface of the water unless there is an opening to let it escape and let fresh air in.

 

[TwoTankAmin]

I doubt one can seal a tank completely without making some major alterations. They how do tou deal with feeding and maint.

From day 1 all of my tanks had had decent lids. The goal is not to prevent gas exchange to but to limit fish exiting without permission and to minimize dust etc. from the air settling on/in the water. In many of my tanks the lights sit directly on the top glass. I do not use land plants with roots in tanks. When I was cranking out plecos their tanks had no lights on unless I needed to work in the tank. Only ambient room light or what cam in via windows was available.

I cannot imaging working in tanks or catching fish with a mas of roots from land plants in the way and difficult in getting to things I needed to be able to manipulate. I want clear access to as much as possible via the top of a tank.

Since I want back to using floaters which multiply faster than convicts or live bearers, there area a couple of tanks where I have to remove the floaters to a bucket so I can work in the tank.

It would be extremely difficult for any filter to do its job if we wanted to seal a top so it cut of all gas exhange potential. If it were possible to do and one used air powered filters you would likely pop a tank the way a balloon exploded when it gets over filled with air? More likely it would prevent the air from getting is as the internal pressure would be greater than what an air pump can generate.

I think of one wanted to seal a tank lid to the prevent gas exchange one would need help from NASA to make it happen.

 

[Tomsfish]

There are many examples of sealed ecosystems on youtube. Most do them in jars.
If you have live plants then all things should balance out to some degree I imagine.

 

[Magnum Man]

so I wasn’t implying about silicone sealing a glass lid on, more likely just a tight fitting heavy glass lid, that fits tight into the frame recess, as has been slightly discussed the bulk of the oxygen comes from surface aeration, the bubbles do little, and if there is a limit to the exchange of atmosphere air in the tank ( that fraction of an inch of air at the very top
of the tank, under this glass lid ), and that space ends up with less oxygen than what is normally there, the fish are likely to suffer… so, even though we don’t like evaporation, reducing that to a minimum may oxygen starve the tank???

 

[WhistlingBadger]

I suspect it would have to fit very tightly indeed for CO2 and oxygen not to diffuse from high concentration to low. Add to the fact that you've got a constant inflow of fresh air from the bubbles, and I don't think you've got anything to worry about.

 

[Magnum Man]

I would guess the fill line ( air thickness at the top ) may make a difference… between a 1/4 inch air gap, and an inch and a half, is a significant volume difference…

since I have American Frogbit in this tank ( it’s larger ), I will likely have at least an inch of air, for the frogbit to stretch it’s legs???