By Bob Goemans
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Bob Goemans corresponds with Steve (LeRoy El Cerrito, CA)

Steve (LeRoy El Cerrito, CA) writes...

Dear Bob,

I just finished reading your book "Live Sand Secrets" revised 2nd Edition. I'm really excited about trying a plenum system on a 24-gallon nano cube tank. Dimensions roughly are 20" x 20" x 18"high. I've tried to follow your articles over the years and recently read where you recommended to someone else who had a 12-gallon tank to just use 1" of live sand on bottom of the tank. I don't know if anyone else has tried this with a 24-gallon tank before. My humble thoughts on this are, wouldn't it give you much better stability on a smaller tank regarding fluctuations of pH, calcium levels, etc., especially when implemented with the aragonite sand? It might solve some of the problems associated with nano reef setups. The only problem I could see is the height of the plenum, egg crate and sand, which would equal about six inches. Or do you think I'm wasting my time on a tank this small? I hope not.

Also, I can't seem to find Live Aragonite Sand in your recommended size of 2 - 4mm. I went to the CaribSea website and they recommend their special grade reef sand (list of products) size 1 - 2mm for plenum systems. Wouldn't this size be too small or am I just reading it wrong? You also mentioned a company that makes ready to use plenum grids. Do they have a website I could go to out of curiosity? I've also been emailing the manufactures of the Wave2K wavemaker about making a custom wavemaker for my aquarium that would fit on the back wall between the overflow skimmer and the return. (Another great product in my way of thinking) Do you think this would be too much turbulence for the aragonite sand? Possibly moving it around, etc. What would you recommend as a cleanup crew for this size of aquarium without disturbing the sand too much? I keep reading about quantities of hermit crabs, snails, etc that seem a little too much in excess. Not to mention the extra bioload added to the system. Lastly I've tried looking through some of your past articles and was wondering (Couldn't find), on whether you preferred metal halide or compact fluorescent lighting over your systems and if you felt that it made a difference or not with regard to the plenum.

I guess reading your book just opened up more questions for me. I've had reef tanks before but never had the chance to try this before now. I've always thought that you were on the right path and that there had to be a better way to manage a reef tank. I know these are a lot of questions and that you are a busy person, but any help would be greatly appreciated.

A fan from the beginning,

Steve LeRoy

El Cerrito, CA

Bob replies...

Hi Steve,

Good letter, and the reason I recommended a shallow bed in that 12-gallon nano tank was simply that a bed of about five inches would distract from its appearance. Usually, the goal with nano tanks is to display a small environment with appropriate sized creatures. And a 5-inch deep sandbed in such a small tank would have shifted attention to the bed, instead of its creatures. Nevertheless, if that's your goal, i.e., to focus on the value of the bed processes, then go for it. In fact, it would be a good learning tool, and know of one plenum system that is now about 12 years old and still doing wonderful with never a sign of any unwanted algae.

As for a plenum system maintaining alkalinity/calcium levels, that all depends upon the system's bioload. If the draw is more than what dissolution of calcareous materials can provide, then I recommend the use of any of the fine two-part liquid calcium/buffer additives on the market for these small systems. In fact, would go that road from day one using the recommendations on their labels to be sure the important pH, alkalinity, and calcium parameters stay within the proper ranges, as nano tank water quality is more difficult to maintain because of their small water quantity.

As for your tank, quarter-inch supports and quarter-inch egg crate would suffice, with a 3 - 4 inch bed on top of the grid. One inch less of sand, as with a 3 inch bed, would equate to a loss of about 30% of its anoxic area, but still provide enough efficiency if the tank is properly maintained. And as for the proper size sand grains, I've been using/recommending that crushed coral be used, as that generally falls into the 2 - 5mm range sized particles. And CaribSea provides a 'live' product that I've used in many past systems. As for aragonite not being available in this grain size, that's true, or at least I don't know where it may be available. However, years of personal research has shown that beds consisting of particles larger than what was originally used in testing plenums, i.e., 1 to 2mm, provided improved porewater sites and diffusion, which in turn improved bed longevity/processes, especially so in beds that were somewhat mismanaged. And as for the solubility difference between crushed coral and that of aragonite particles, the difference can be easily be made up with the use of the two-part solutions. And note, the company that made custom-made plenum grids has gone out of business due to the poor health of the owner.

As for the Wave2K wavemaker, the test unit sent me and set up at a local shop on a 125 gallon system proved so successful, the owner took it home on put it on his 600 gallon aquarium! As for its lower wave action cycle, I would suggest the unit set on a couple pieces of rock so as to elevate it a little distance from the bed, or the unit built with a deflector that causes the outward bottom flow cycle to be slightly deflected upwards. And keep in mind, if they do build a unit for your system, do not place high reaching obstacles, such as high piles of rock or corals that would block the wave action across the aquarium, as you're defeating part of the cycling process. Carefully plan your environment so as not to cancel out the back and forth wave motions.

I agree that the use of clean-up crews is often overdone! In a fairly new set-up your size would recommend about six Astraea snails, a few hermits (blue and/or red legs) and one small brittle star. If your bioload greatly increases, then add some more snails and hermits.

When it comes to lighting, my choice of metal halide or fluorescent fixtures depend on what animals are in the system. But where you're concern, you'll have a very shallow environment, and fluorescents should be able to fulfill your needs, and besides, run a lot cooler than MH's. And furthermore, the intensity of the lighting will not affect the microbial processes in the bed. But, would suggest blocking light penetration into the lower 'plenum' area from around the outer sides of the aquarium, as it may initiate some algae growth because of the nutrients cycling in this area. Wooden furring strips, or black electric tape will do the trick.

For a lot more information, visit my website at



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