Could you use masking tape to tape that plastic mulch or plastic drop clothes (which would be thicker and maybe better at stopping drafts).? There still are those 3-M plastics, though maybe a little more expensive.

We still have a residual of the masking tape on the fishroom windows. I should have been quicker to get that stuff off in the spring. I now have a mild solvent to dissolve the tape marks, but will wait until spring in order to ventilate the room.

"So, I can really plexi over the tank without harming anything?"

Sure! Measure and check first for scraps with your local hardware store.  I would investigate the smaller places first. With the kitchen windows OPEN, you can take a large nail and a pair of plyers and heat that nail. The hot nail can be pushed into the Plexiglas, burning a hole for feeding and for the airline. If those holes are burned more towards the middle, there is even less possibility of the fish jumping out through them. (Maybe a summer project though). It is a liitle sloppy, but one can run an airline under the edge of the Plexiglas. Wipe any oil or solvent off of the surfaces!

Um, old tank sides may work well too. I have several Likewise old window panes, well wipped off, can be useful that way. Be careful to wear leather work gloves when preparing those items. The window glass may be brittle.

Even have some window glass from a shopping center. That is thick and strong too! Seems there had been this anti-war rally in 1970 which went local in terms of issues...

"I suppose that would help with my MASSIVE winter evaporation issue, too..."

You betcha! That can even be a life and death issue for the gups if the water gets too hard through evaporation and the addition of tap water. (Yep, see the Immediate Help entry on Winter Mystery Deaths.)

One could even use one of those better kitchen plastics to tightly seal the top and really hold in the heat and humidity. Tiny holes can be punched. Be careful not to forget how flimsy they are and set a jar of water one it though! (You know how I know.)

I need to do more stuff like that when I get my fishroom blower up and running again. Do NOT want a humidity problem in the house! Actually that is a linear piston pump, supposed to be the cheapest to run many tanks with.

Keep warm! :)