Oooookay.

The key thing to remember about bioconversion (or biofiltration-same thing) is that it does only one thing. It converts toxic ammonia from our fish into equally toxic nitrites and from there to relatively non-toxic nitrates. Nitrates are fertilizer, and will serve as food for plants, INCLUDING ALGAE! Nitrates are reduced with water changes and aquatic and marginal plantings. Floating algae will not be cleared by a biofilter! You need an Ultra-violet unit to do that. Hair or string algae is another problem, and is the product of ammonia, phosphates and sunlight. The only safe solution for hair algae is a soft scrub brush.

The other thing that a filter should do is *mechanically* filter your water, removing particulate matter from your water. Filter mat, bead, brushes sand, gravel all work at varying degrees of efficiency and ease of cleaning.

When setting up a biofilter, your goal is to deliver the entire volume of your pond through your filter at least once (and preferably twice)an hour. That means that your filter has to be able to accept that flow rate comfortably, without leaking or overflowing, and allowing the water enough contact with the filter media to do an acceptable job of bioconversion.

A pump rated at 4500gph may not actually deliver that volume! There is loss of flow from the resistance in the pipe runs, as well as loss from pushing uphill and turning corners. If you go to the website, you'll find directions on the articles page to tables that will help you calculate just how much flow you are actually delivering through your system. It'll be way less than 4500gph, I assure you. If your pond contains 4500 gallons, your pump is not powerful enough!

Remember that a biofilter is just a box filled with stuff for the bacteria to sit on while they work. You may find it more rewarding to build your own.

Bob Passovoy
President
MPKS