CichlidFish.com - Fish That Think.

I'm trying to figure out how to filter the big tank I just made.
Maybe someone will have some ideas on how I can do it? With what I have? or other cheap suggestions?
So far I'm working on filtering the 400 since it will probally be the hardest to do.

The Idea I have is to filter it with a pool filter - a 3 gallon sand filter to be exact. (its all plastic so its safe,I used it once before) and I was also going to turn a 120 gallon cattle trough (large metal tank/water safe) into a combination wet/dry - sponge filter .
If I run a set up like this since the pool filter is mostly a polisher (sort of like a fluidized bed filter) should it be put before or after the wet/dry ?
Either way one will have to run on a gravity feed type system, is there any easy way to figure this (match it to the pump)? So far I was thinking multiple runs of 1 1/4 pvc with ball valves ? But maybe theres an easier way I'm over looking?Would it be easier to gravity feed the tank or the filter?

I've also debated trying to plumb it in some way that it would do daily water changes itsself,with a gravity or line level type of drainage and some kind of ballcock(like older toilets) type system to fill it. Anyone have an experiance with this type of system,if so does it have any pros or cons versus normal filtering?

While I'm at it - whats some oponions on heaters for a tank this big? I'm considering either a "fireplug" type inline with the filter somewhere or an 800 watt submersiable Titanium, so far. I often see people on boards saying use two or three smaller heaters - but I talked to a rep for both whisper and visitherm and they advised against this saying it leads to premature failure and disrupts the thermostat.

i think that 2 800 watt heaters would be good.