Q. I'm new to the hobby of marine fishkeeping and this magazine appears to be the encyclopedia that I will keep for years as reference. It is very welcome at my residence. Your team provides very good information for people like me. Keep up the good work.

I recently built a 108-gallon reef aquarium (60 x 24 x 18 inches). I used six fluorescent lights (48 inches, 40 watts). Two of them are Aquatinic tubes that provide a white light, two are Power-Glo tubes and two are Marine-Glo tubes. The lights are located about a foot from the surface of the water. Both Aquatinics come on together for 12 hours. One Power-Glo and one Marine-Glo are on for seven hours, and the other two for four hours. Is this a good setup or should the last light be on longer? Are the combinations okay?

Right now, there is brown algae growing on top of the crushed coral sand that's starting to turn green. At the pet shop, I was told that there would be a cycle of brown and then red algae, and finally green algae. After the cycle is complete, will the sand return to being white? Also, what are the gas bubbles produced by the algae?

A. It is perfectly normal for an aquarium to go through an algal cycle when first set up. In fact, these cycles can take several months, even up to a year. Live sand systems often go through longer cycles — usually a brown or red cyanobacterial film will persist in some areas or cover large expanses of the sand. These growths will eventually disappear, and once they begin to recede they tend to do so rapidly.

There are a couple of possibilities to explain this. In some cases the composition of the substrate may be such that it is high in silicate or contains a lot of chemically bound phosphate. When these nutrient sinks are exhausted by overlying algal growths, the algae become nutrient limited and begin to recede. Another possibility is the live sand bed does not yet contain microorganisms in appropriate amounts that feed on these algae. Once their numbers build up enough, the algae is quickly consumed. That is why some aquarists have suggested adding a small amount of live sand from an established system to one with algal growths on the substrate (J. Sprung, personal communication). This often results in a gradual decrease in undesirable algae growing on the sand as, presumably, the microorganisms on the introduced sand grains spread throughout the sand and consume the algae. These are only theories, and the exact cause remains to be determined. The gas bubbles you are seeing are most likely the result of photosynthesis, and are probably oxygen.

Although the lighting is adequate for many of the lower light corals, I would recommend that you cut down on the amount of red or pinkish tint. It's okay to have one reddish light, but the others should be lamps that give a greater white and blue mix. I would recommend having all six lamps on for more than four hours — six or eight would be better. I would also place the lamps closer to the surface if possible (say six inches).

Retreating Coral
Q. About a month ago I purchased a green open brain coral for my 10- gallon mini-reef. About three days ago it retreated and hasn't expanded again and I'm trying to figure out what is wrong. I'm using a skimmer and 15 pounds of live rock for filtration, and two 15-watt lights (an actinic white and an actinic blue). I've got various mushroom polyps, which are all rapidly multiplying, and a fox coral that is doing quite well. The only other tankmates right now are three shrimps, some hermit crabs and some turbo snails.

Ammonia and nitrites are zero and nitrates are below 10 parts per million. The pH in the tank is about 8.4 and the temperature is between 76 to 78 degrees Fahrenheit. I change 1 to 2 gallons every month and add Combisan and magnesium supplements. I also add a Seachem calcium supplement. I use activated carbon for two or three days a month.

The coral was doing well and fully expanding for the first few weeks I had it. One small area that was damaged (necrotic) when I bought it was almost healed. Then I needed to finally remove my green goby and purple firefish for a month to quarantine them in a tank treated with copper for marine ich. I had to move the green open brain coral in order to catch the fish. The coral receded and hasn't expanded since. Basically, I'm at a loss. Is it normal after being disturbed for a coral to retreat for three days? What about the two "ribs" on the edge of the coral that have whitened?

A. It is not unusual for corals to remain retracted for a few days after being moved. Oils from your fingers, abrasions of the tissue and different water currents and light levels in the new location can all cause such a response. If the mushroom anemones are touching the coral it is possible that they could be stinging it and causing the coral to remain retracted.

The fact that the tissue is actually receding in some areas so that skeleton is showing through is indicative of damage to the outer epidermis of the coral. Usually these areas will heal quickly if the coral is healthy.

Have you tried feeding the coral since it receded? If not, this may be a way to encourage it to expand and may speed the healing process. It is also important to keep the bare skeleton free of algae — you should gently remove any algae that may begin to grow on it.

A 10-gallon tank is awfully tiny given the amount of rock you have in it, so I am not surprised to see that the water temperature fluctuates. If you can eliminate these fluctuations you should see a decrease in the frequency of ich outbreaks in your system.

A Reminder
I've said this before, but it's worth repeating. In reading through the letters and e-mails I often wish I could receive more information on the systems being discussed. There are certain parameters I would like to know about when you send me questions.

Let's start with the tank itself. How big is it and what are its dimensions? How much total water is in the system including the filtration system? Where is the tank located?

How many lights do you have? What type are they? What is the wattage, color temperature and length? How often do you replace them? How far above the water are they located and is there a shield between the lights and the tank?

What types of filters do you have? If you have a protein skimmer, what size is it, how much water are you sending through it and with what type of pump?

If you are using activated carbon, how much do you use, how often is it replaced and where is it located? If you have live rock, how much do you have, how is it arranged, how old is it? How did you set up and cycle your system?

What additives do you use, how much and how often do you add them? If you use calcium supplements, how do you prepare them and how are they added?

How often do you clean your filter system, the glass, the aquarium and the prefilters? Do you do water changes, and, if so, how often and how much? What type of freshwater are you using and where does it come from?

You should provide me with the following measurements: ammonia, nitrate, phosphate, pH (range), alkalinity, calcium, temperature (range) and specific gravity. Iodide and strontium levels are also useful to know, but not critical.

Finally what do you have in your tank? What types and how many fish, corals and other invertebrates do you have in there? How large are they and how close together are the corals? When were they added?