I'm building a sump out of a 20H. There is pre-cut glass (I think 1/8") at Home Depot that seems like it would work. Otherwise they have the Optix brand acrylic but it seems flimsy. Any suggestions?

1/4". 1/8 is to brittle.

1/8" would work just fine.

be careful of sharp edges

i use the stuff at lowes... just cheap plate glass 1/8th I think and it works great!!!

use the cheap stuff from home depot it work just fine

If worried about water pressure on it, keep in mind the pressure on both sides is equal, and glass has pretty amazing compression strength.

just don't bump into it with anything - skimmer, return pump, etc. also, as mentioned, watch for the sharp edge.

True that ^^. Amazing compression strength, fairly poor tension strength.