Hi all, first post on the forum, looking forward to being part of the community. Well, I need a little advice for a multi-tank project I'm working on. It's challenging for me, but has been fun (mostly) so far. I'll give a brief summary and what I'm having difficulty with. 1) 4 - 20g long aquariums stacked, 3 DT tanks, 1 sump 2) Original idea, which I've done, is chain the tanks together, the topmost draining into the tank below it, that into the one below it, etc. 3) I used 3/4" bulkheads. I now know I should've gone with 1", but for how much flow I wanted through the sump (100-200 GPH) I thought 3/4" would be fine. 4) I tried to go with the simplest setup possible...single rear-drilled drains with internal overflow box on each of the DTs. Simple in theory. Execution, not so much. 5) Siphon occurred on startup, resulting in super loud system. Ran some airline down each tank's drain, quieted things down. 6) However, flow is not great and return pump had to be turned down. I believe this is due to the fact that each overflow box is draining into the tank below it, and the outlet of the drain is submerged in 3-4 inches of water. Not a true unrestricted drain. 7) Other side effect...using a single line drain between each is resulting in bubbles I will never eliminate. Starting to re-think the setup. Moving forward: I have received some advice, a few of whom said blow it up and start over. Drill double drains, bigger overflow boxes etc. To be honest, my budget has been basically reached for this project system. It's in my unfinished basement sitting on a floor drain, so my fear of damage from potential clogging down the road is fairly minimal. My thoughts are this, switch the overflow box on my middle DT to line up the drains and returns. This would eliminate the bubbles being blasted into each tank and also maximize the drain GPH rate of the drain line. My biggest questions are...if you look at return pump side drawing, where should I put control valves to effectively control flow to the 3 tanks? Above the top T and between the T's, or should the valves go to the "left" of the Ts? Also, for the drain, would I be able to run all the drains into one line with T's (T's placed similar to return line, or would that result in tanks draining into each other), or should I use Y fittings as in the drawing? Any advice (other than start over!) would be greatly appreciated. Thank you!