Here is what Dark Rivers Hatchery is planning on using to filter 3 1800 gallon fw stingray indoor ponds read the link
http://www.macarthurwatergardens.com/Aquabead/aquabead_plus.html
the Medusa solves the age old problem of how to filter a large pond while only using one filter. The problem: Pond is 20 to 25 thousand gallons. You want to turn it over about every 2 hours. A 1/4 hp pump will put out about 5000 gallons an hour.
This means you need two filter systems to accomplish this and stay with energy efficient pumps or a giant pool pump moving 10,000 gallons an hour and costing you an arm and a leg in energy costs.
The Solution: Medusa
With this filter you can run two 1/4 hp or two 1/3 hp pumps and only pull about 5 amps total with the 1/4 hp pumps or 7.6 amps total with the two 1/3 hp pumps.
The Medusa is designed in such a way that all valves and internals of the filter are double that of a regular filter. At no time does each pumps water pathway get smaller than a 2" opening.
Every thing is double on this filter so that we maximize the flow potential of each pump. Everything is double on this filter except the price, you'll spend less money on 1 Medusa than installing 2 individual filters.
The Medusa is designed with the same integrity as the AquaBead filters. Designed to maximize the flow and efficiency of today's modern koi pond pumps.
We remain committed to providing the most energy conscious filtration products in the industry. The Medusa will let you filter a 20,000 - 25,000 gallon pond on a total of only 5 amps!
listed at bottom on page on link .
The medusa has a flow rate of about 250 gpm which is great and can hook into a in line heater that keeps things nice.
Our vats are 15'LX4'WX4'TALL
let me know what you think
Jason