I didn't realize I had never posted this here. Last May, I decided to take a crack at building a custom sump for my 125. I had been using one that was originally built for a saltwater setup as it came with the used 125 I bought from Craigslist. It worked okay for three years but I felt I could do better. I scoured the internet for examples and made the decision to make it completely out of 1/4" polycarbonate. I chose polycarbonate as it's cheaper and stronger than plexiglass. The reason it's not used in tanks as poly starts to get hazy at around 1/2" thick. I went with the basic design below but made some changes to fit my application. Altogether, it took about 13 hours to complete the construction.