>>950513You can see part of the main filter in the pic I poasted of the whole tank... by the overflow pipe there's two big powerheads. They pump through home-made reverse-flow undergravel plates under ~3" of crushed coral and sugar oolite. I'm aware of the problems with UG filters, but for a heavily stocked fish tank I find that the biological filtration is essential. Also I set the sand-bed up just like you would for a Jaubert plenum, so if I decide to switch it to a reef tank I can just pull out the powerheads and cap the plumbing and after a couple weeks it's good to go.
I have a second bio filter in the sump, just a 2.5 gallon plastic bottle full of sand with a powerhead pumping water through it, nothing fancy.
skimming is handled by two home-made countercurrent skimmers slapped together out of 2 liter bottles, an empty peanutbutter jar and some pvc pipe. Pic related. They sit inside the sump, fed from the overflow pipe. I have them in 5 gallon buckets to keep the water level constant to the skimmer even if evaporation or leak lowers the water in the sump. They drain about a quart of green/brown skimmate every month. I have them set to skim wet and drain to the sewer, so all I do is clean and check them every few months.
the rest is mostly store bought, a couple cheap UV lamps, air pumps, ozone for if the water gets acidic, cheap heaters, powerheads and return pumps. Instead of buying one large component I'll buy several cheap ones and replace as necessary. That way if something breaks it's no big deal and doesn't much affect the system before I can change it.
I have really hard water with no nitrates or phosphates, so I just use it straight from the tap after dechlorinating. I do have an RO/DI unit I used to use for discus tanks, but I haven't raised any soft-water fish for a few years now. I decided a while back to use the water I have for what it's already good for, and it comes out of the tap perfect for seawater.