I may get shot down for this but I use Saran Wrap on my 10gal quarantine tanks. I didnt want to spend $ on a glass top nor set up an auto top off. I got tired of filling jugs and using drip sets to replenish(I try to keep my fish seperate for 2 months). I do use airstones for fresh air and I do leave a small opening for air to escape. The saran sticks nicely to the outsides of the tank. I have the saran not extremely tight but droopy in the middle which allows condensation to drip back to the tank. I needed to cut down on evaporation which was causing fluctuations in my salinity that new arrivals didnt need. I also was happy to see that when new arrivals tried to jump they only hit a soft barrier vs. hard plastic eggcrate. I wouldnt recommend this if you have a light above the tank. I indirectly light my quarantine tanks.