Bob replies...

Dear César,

Thank you for your kind remarks and let me note that I prefer to be addressed as 'Bob' not Dr. Goemans. My doctorate is not in the medical field, and feel that 'Dr.' should be more properly applied to those with a medical degree.

Let me address first your decision/question to place the plenum in an interconnected tank, i.e., auxiliary plenum system. This method has become widely accepted, as many aquarists simply do not like the look of a very deep bed in their main system. Not only has it resolved that issue, it is proving to be more easily maintained when not cluttered with live rock formations and various coral animals. My old 180 gallon solar powered reef aquarium had a 60 gallon plenum tank under the main tank. However, that main tank had 27 fishes and was fed as many as six times a day. I found that size interconnected plenum system not capable of keeping nitrates below 5 ppm, as originally desired. Its nitrate level stayed about 7 to 8 ppm. Therefore, it only seems reasonable to assume a slightly bigger plenum system or less feeding would have reached that goal. Because of this personal experience, I now think the interconnected plenum system not be any smaller than half the size of the main tank when it comes to surface area. And yours should do nicely! Of course many aquarists don't feed that often, but I couldn't pass up all my little friends every time I passed by without giving them a treat. Besides, I was using a new phosphate removing product from England called ROWAphos that is quite remarkable. I was also using the Merck Test Kit 1.14445.0001, which is without doubt extremely accurate. Keep phosphate below 0.015 ppm and you'll never be bothered with unwanted forms of algae! And this is the only somewhat reasonably priced kit that I know of that will accurately measure this extremely low level.

As for flow rate between the plenum tank and main system, feedback and personal experience show that something near half its volume per hour seems to work the best. If your auxiliary plenum tank is about 80 gallons, then forty gallons per hour should flow between them. Again, this seems to work the best for everyone that has tried it, yet flow could be somewhat more or less.

My preference for makeup water continues to be just plain RO/DI water, with no additives. I am not comfortable with the wide array of additives on the market. Not because they are of inferior quality, but because of improper use! Too many aquarists think a little more is better when it come to dosage rates. Not true, and confusion remains about their need. Often, there's duplication of various elements and compounds and that leads to precipitation of much of it. And, if there is a calcium reactor in use, much of what would be added to RO/DI water is duplicated in the reactor's effluent. Yet, in certain circumstances, these RO/DI additives do have a good value, however, each system should be evaluated as to their need.

When it comes to the three available skimmer brands, I or my clients have or are using all of them. They are all excellent products, however, you are right about the more plankton safe Tunze models. If that's a concern, the Tunze model would be an excellent choice.

When it comes to the depth of the sandbed in the show tank, I've done almost the same thing in my old 180 system. In some places it was about two inches deep and sand grain size was about 2 mm.

As for lighting, your six foot system will probably need three 250W 10K MH lamps and possibly two full length 50/50 type fluorescent lamps to adequately light the entire tank. However, for now, more light loving corals could be grouped near the two MH lamps and those animals not needing bright light placed in the lower light areas. It all depends upon your ability to pay the electric bill! And I've found the 20K lamps to make the environment look too blue. I prefer the 10K's. Of course either would suffice for the animals, but to the human eye, my preference is the 10K's.

When it comes to powerheads, I've grown to like the various models in the Tunze line. I've had great success with them, however, they are quite pricey when compared to other brands. As for placement, the rear corners are two of the best places with each facing forward and slightly to the center of the aquarium. Placing them on a wavemaker so as to alternate their flows is the best approach, and the Tunze units are built to handle the on/off routine without any heat buildup or additional wear. My reef system also used two Tunze Turbelle 3000/2 system pumps for consistent water movement in the aquarium. With each Tunze capable of delivering about 700+ gallons per hour, system surges could at times exceed 2000 gallons per hour. And that's not counting the flow from my interconnected plenum system. That entire system can be seen by visiting my new website at www.saltcorner.com and clicking on the Photo Gallery button (the lower right button). Which by the way could contain system photos of your system (or others) if they become available to me.

I should also note the flows that impact the animals must be related to what they would incur in the wild. That's not easy to judge, but commonsense should be used. System overall water movement is more of a general concept that helps with preventing dead spots and providing good gas exchange. It should never be confused with direct flow against or around an animal.

As for 'live' plankton foodstuffs, I'm not sure what's available in your area. Yet, caution must be used when using any live foodstuffs as unwanted organisms can easily be introduced. My preference is would products such as Julian Sprung's Marine Snow, Marc Wiess Combo-Vital and/or Kent Marines Chromaplex Phytoplankton/Phytoplex Phytoplankton. Also there is a new phytoplankton product called BioPlankton from Liquid Life USA. You can check it out by visiting my website and clicking on their banner on the advertisers page.

For starting the microbial processes, there are many excellent products. And if possible, an aquarium's sandbed should be microbially well established before adding too much live rock. Starting a system with more nutrients than what there is in the way of bacteria to use them simply does not make sense! Why give unwanted forms of algae an opportunity to gain a foothold. Get the nutrient 'users' established first, then introduce a supply of their needs. Patience pays off in the long-term! And, could be the sand your going to order is available 'live.' Some of these prepackaged brand sand grains are already coated with bacteria. Even though dormant, these bacteria will quickly awaken and begin colonizing the substrate. Check it out!

Hope this helps and keep me posted,

Bob