Bob replies...

Hi Stanley,

Thanks for the follow-up and things here at home are fine, but things in our country could be much better! Why can't people just help other people, no matter who they are, have a better life?

To clarify for the readers of this column, what was said was to siphon out, as necessary, the sandbed surface algae if it becomes mat-like. With that will come some upper sand grains that are attached and, that it's quite normal for some algae and/or cyanobacteria to flourish in any area where light and nutrients reside. That would include the sandbed side areas facing outward at the aquarium side panels and especially the sandbed/bulk water interface.

As for your questions, rinse the sand and reuse it. If possible, place the rinsed sand in some vinegar over night, then rinse again and reuse it. Any adhered phosphate will be removed. The forming of some surface algae, whether brown or green during the initial colonization of the sandbed is to be expected since it's a highly active microbial zone. The initial ammonia/ammonium present at this interface is almost always quite high and can lead to the situation described. In reality, it's really a good sign that the microbes are busy doing their thing so to speak. The major portion of algae/cyanobacteria should become less and less as the bed matures. Yet some, depending upon bioload and husbandry practices may continue. But should not be looked upon as a negative unless it becomes mat-like. If it does become mat-like then system husbandry, such as feeding/bioload and/or water quality need to be reviewed, as would be the case in any style filtration system. As for the cleaned sand, it needs no other treatments as the top-most surface area is always the most active and/or quickly reestablishes itself naturally. Try to maintain a bed depth of four inches when using a sand grain size of 1.0 to 4.0 mm. If slightly larger, go to a depth of five inches.

As explained in my last letter, too much live rock can result in other nitrogen products, such as ammonium. Nitrate itself might be somewhat lower, but algae prefer ammonium! As for now, your bed is still not fully developed, and present nitrate level should go down in the near future. However, other parameters such as diet, bioload, protein skimming, sandbed maintenance (vacuum upper inch and check for any binding) need to be addressed, as they would in any style system. Also, check the nitrate content in the water being used for water changes/evaporation makeup.

A UV sterilizes the water passing through it and thereby kills such entities such as floating microalgae, bacteria, viruses, etc. Much of that is food for corals. Their use in fish-only systems can be quite beneficial, yet for reef systems, no matter what type filtration system, they are generally not used.

I recently met the author of the article in question at MACNA in Baltimore. He's actually a salesman for an aquarium product company. We chatted in a polite way and was told that what was said were the results he had from his try at the plenum method. During the course of the discussion I mentioned the thousands of very successful plenum system worldwide, with one now established almost eight years and now better than when it was originally set-up. However, that and other mentioned actualities did nothing to change his mind. Hopefully you read Julian Sprung's column 'Reef Notes' in the October FAMA, where he countered some of the comments made in that article. Hopefully this answer's your question on system longevity in closed systems.

If you would like to see some photos of my aquarium, visit the photo gallery section of saltcorner.com!

Hope this helps,

Bob