I was going by this set of instructions for the Nu-Clear filter: http://www.inlandseasproducts.com/v/...structions.pdf

It says:

**RECOMMENDED PUMP**

Use with a pressure rated water pump rated at 7 to 15 PSI, or at least capable of handling 14 ft of head pressure with the desired flow rate. Suggested flow rates are a minimum of two times tank volume per hour for freshwater tanks and four times tank volume per for saltwater tanks. The pump should be able to supply the desired flow rate at a nominal head height of 12 ft. Pumps should always be installed in line before the filter(s).

Reading that again, it mentions both 14 ft of head pressure and 12 ft. head height. It also mentions 7-15 PSI, which is equivalent to 16-35 ft. of head (according to http://www.engineeringtoolbox.com/pu...ure-d_663.html). Quite confusing.

I suspect that all of this is just rough rule of thumb stuff. Technically, your pump is under-rated according to the Nu-Clear people. You'd like 1000 GPH, so they ask for a pump rated at 1000 GPH at 14 feet of head. Your pump is rated at *zero* GPH at 14 feet of head! But, I expect that their recommendations are very conservative to allow for a sizable safety margin for very clogged filters. If Nu-Clear became known as the filter that clogs easily, their sales would suffer.

This makes your empirical experience so valuable. We know that the Pan World 50PX-X is adequate in a system like yours, maintained as you've described.