To cover or not to cover?

A majority of my tanks are always open-topped.:grinyes: I have notorious escape artists even then in there. *whistles* *knocks wood*
 
i actually have a great solution for this:

i had purchased some light-diffusing "eggcrate" from home depot to put under my gravel and rocks in my 55g african cichlid tank-- it's supposed to spread the weight of the rocks and prevent puncture/cracking. it also prevents the gravel from shifting much, which was a nice if unintended benefit. anyhow, the 55g is 48 x 12" roughly, and the sheet (about $10?) was 48x24".

so after i did the bottom i had an equal-sized piece left over. a lightbulb went off in my head and i cut it into two pieces (my 55g has a center brace) and I use it... as a light diffuser for my coralife aqualights! it's open and allows moisture to escape, while preventing jumpers (the spaces are about 1/3" square, all my fishes are much bigger than that). i don't mind topping off, and at least during the winter using my tank as a living room humidifier isn't a bad thing!
 
Mine are only mostly covered, I don't use the plastic strip along the back. I find maintenance easier. The only fish I ever had jump were many years ago when we tried to cover completely. The jumpers will find a way, up the HOB, by the heater.

I do sometime leave the water level down a few inches when adding fish more apt to jump so they can learn the tank for a month or so.
 
How does this affect labyrinth fishes? I have a fairly tight fitting cover on my paludarium w/ a Betta. I'm reluctant to leave it fully covered because I 've read they need fresh air.
 
If the tank is totally sealed (and not heavily planted), then I would think oxy deprivation will eventually kill the fish, or impair bacteria respiration to cause an ammo spike (crash). Gouramis and such can take some O2 from the air given they've evolved to live in O2 poor water (pretty sure that's correct), but if the air above the tank is also stale.....

Well, if you ask my cats, they prefer tanks uncovered. :-)
 
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