Hi all, I wanted to share the construction of my AP project. It will be a CHIFT PIST setup with flood&drain using two autosiphons (one for each grow bed) and a valve to toggle flow between the two GBs. I will include pictures and prices and be happy to answer any questions.
I located a 50 gallon aquarium on craigslist for $20.00. Wasn't too bad, kinda dirty, gave it a good cleaning with ammonia. It was fun finding a diamond hole saw, and I wasn't about to wait for something in the mail. True Value had a 1 3/8 diamond hole saw (Brutus No. 10569 - it doesn't say it works on glass, but it worked great $21.24 [total to date 41.24]), with a guide and some doubleback sticky tape. I must admit, the thing worked like a charm. Highly recommend.
Place the tank on it's side (tall wise) drill the hole from the inside of the tank so that you have a smooth surface ensuring a good seal. the two sides are much thinner material than the long piece of glass.
When drilling, do not apply much pressure, let the drill do the work. Be extra careful towards the end, so that you don't chip alot of the hole's outer edge.