i went to lowes about 1 or 2 month sago and they cut glass for me, but i recommend using a normal fish tank for a sump, i have a 29 gal prop tank as well, and i just took a 10 gallon tank and had glass cut for the walls on the inside and siliconed them in. The reason i suggest this, is that they can only cut/carry like 1/10 inch glass or something insanly thin like that. And obviously if you use glass that thing, the chance of breakage is high. And i dont believe its tempered.