I made something like that for my first ball clutch. Only out of a 10 gal fish tank. Covered with a piece of glass. Work pretty good i had 3 out of 4 eggs hatch. The one that went bad didnt look good when i found it. Now i do the old fridge thing with 4 foot of 11 inch heat tape on a Helix. The tank thing worked but i feel better about the fridge on the Helix. Also it will take me some time before i need to get something bigger. The only thing i didnt really like about the fish tank setup. Was that i was always adding water to it. The heater needs to stay under water all the time so it dont burn up i guess. With what i use now i only had to add water once in 60 days. I had 95% to 97% humidity the whole time.