The tank is a 72 gallon Bow Front. The water side
holds 15 gallons of water. There is an overflow built in to keep
the water level constant at the height of the land/water divide.
The overflow dumps into a home made prefilter box, then into the
15 gallon sump.
The sump is fully planted with water plants. A mag drive pump
sends the water back up to the tank.
I also use an external Eheim canister filter (just to the left
of the sump in the cabinet). It removes water from the tank, via
siphon, and fine polishes the water, then returns it directly
into the sump.
The return water pressure is constant on 4 valves.
The first valve directs water through perforated tubing that runs
along the back of the tank and into the cave. It helps to flush
out any debris that might accumulate. The second valve is for the
high waterfall. The third valve is for the lower (left) waterfall.
And the forth valve controls a "rain" system over the land side.
The rain system makes water changes very easy, I just open the valve
and "rain" on the land side. The water on the land side is drained
by another valve on the far left of the tank. I drain it directly
into a milk jug for disposal.
The entire system is set up on timers and backed up with a UPS
system (in case of a power outage). The tank timers light the tank
during the day and the sump during the night. This system has worked
out great. During the day (when the planted sump is dark) the sump
plants produce carbon dioxide which is pumped into the upper tank.
The plants in the tank are thriving. The same is true for the sump
plants which gain CO2 from the upper tank at night. The system,
also, works great for keeping the pH level constant.
The water quality is outstanding and both the fish and plants
are thriving. If I remove the overflow prefilter fish eggs will
drop into the sump and I constantly have baby zebra danios and gouramies.