I have been interested in building a sump-plenum for an African Cichlid tank for quite a while. I have read your first book, "Live Sand Secrets," as well as numerous articles of yours over the years in various monthly publications that I subscribe to. I am finally ready to build my plenum but I am confused regarding some of it's parameters as I've noticed that they seem to have changed a few times since the original booklet came to the marketplace.
The actual physical interior dimensions of my tank are: 58.25" Length, 13.75" Width and 18.75" Height (to the overflow slot). It physically holds 65 gallons of water without substrate, rocks, fish etc. My questions are;
What size sump-plenum would you recommend? Footprint/Volume?
What flow rate through this plenum do you recommend?
Could I utilize some sort of a mechanical pre-filter or should I just vacuum the main tank gravel during water changes and an occasional light vacuuming of the sump?
I believe that these are the last pieces of information I need. Any advice will be greatly appreciated.
The history of 'very' successful plenum systems for cichlid tanks goes way back to an experiment that I did for a cichlid aquarium society, probably at least ten years ago. CraibSea donated all the gravel and the aquarists' there recorded all the nitrate levels in the test tanks and compared it to their previous none-plenum tanks. Nitrates where cut by about two-thirds after about six months with plenums in their systems! A very successful test and a bunch of happy cichlid fans!
As for your questions, a footprint of about one third to one half would suffice. As to volume, that would be dependant on its height, and anything with at least four inches of water above the plenum sandbed would suffice. Where flow rate is concerned, a small pump that can deliver about ten gallons of water per hour to the main tank would be all that's required. And yes, a prefilter would be advisable, as cichlids are heavy feeders. And the plenum bed, consisting of sand grains about 3 - 6 mm and a four-inch depth without any dividing screen, should also be vacuumed as you say, but only about once every three months, and monitored for sand binding. If you're in the need of a custom-made plenum grid, contact Todd Schwarz at firstname.lastname@example.org and discuss your need.
Hope his helps, and keep me posted.