The following article describes the result of a 5 month long period of testing performed on a Lobophyllia coral tank, to determine whether high phosphate levels would lead to coral detachment or receding.
This experiment was undertaken to possibly
validate statements made by Peter Wilkens in his book: Invertebrates,
Stone and False corals, Colonial Anemones, and in earlier writings
of his, that such would happen. (Engelbert Pfriem Verlag, 1990, 136 pp.)
The coral was placed in a standard 20 gallon aquarium. Some germane tank information is listed below. The tank (and it's control) were operated with high care and husbandry as one would expect to be the case when conducting experiments. Focus on excluding other variables was high.
Skimming was performed by a Biozone Model 90101, Fluorescent tubing lighting supplemented by actinic light was provided (40 watts + 40 watts). Calcium levels were raised to 470 ppm and maintained there. Temperature was kept between 77 and 80 Fahrenheit at all times. The pH fluctuated by 0.2 pH between morning and evening readings (8.1 and 8.3 and 8.2 to 8.4). dKH was between 3 and 4 meq/l and specific gravity was near constant at 1.023/4.
Filtration was by means of an outside live rock filter, placed in a sump. The skimmer was attached to the sump and drew water from the aquarium and returned it to the sump.
Additives used were: Vital Gold, KSM, Pure Calcium, Reef KH buffer, KW, all from TAT. Kalwasser was added via the drip method and replaced all evaporated water. No water changes what so ever took place on the aquarium and on it's control. No supplemental iodine was added to either tank. Food and KSM provided sufficient iodine for this coral which is not know to need high levels of iodine in the water.
Nitrate and silicate removers were used to maintain their levels low to avoid tainting of the test by introducing other variables. Nitrate in both aquariums was kept at levels below 5 ppm total nitrate and silicate was maintained at levels below 0.5 ppm.
In order to maintain a reference (control) aquarium, another 20 gallon tank was set up under exactly the same conditions, using a coral of about the same size at the time the experiment began.
Wilkens points out that this coral requires moderate to, at times, strong current and this was provided in the aquariums. Small powerheads were used to achieve moderate current. Once an hour, for 4 minutes, a second powerhead would come on and create additional and stronger current in the tank.
Feeding was by means of the addition of a mixture of phyto and zoo plankton to both aquariums, every other day. It is known that this coral feeds mostly at night. The food source was added shortly before the end of the photoperiod and skimmers where shut off for three hours to allow the corals in both tanks to feed. The plankton was obtained from Frank Hoff. After that time the skimmers were placed back in operation.
The only difference between the test tank and the control tank was that the control tank was equiped with an outside filter to remove phosphates. The actual testing tank was not. On the control tank phosphates were kept at a level below 0.03 ppm using a Hach test Model PO-19 to deternine actual levels and add/change phosphate removing compound as required to maintain these levels.
In the test aquarium phosphates were allowed to rise. The reason for the increase in phosphate where attributed to organic phosphate breakdown, leading to the appearane of ortho-phosphate. The sources for the organic phosphate were determined to be: food stuff, invertebrate slime, bacterial die off, die off on the rock and so on. No artificial ways of increasing the phosphate levels were used. There may, of course, have been other reasons. The experiment was not meant to determine what they were but what the impact was on Lobophyllia corals.
Both tanks were monitored for all significant parameters. They were adjusted in both tanks to keep them as close to each other as possible. Only PO4 was allowed to rise in the test tank. In the control phosphate was removed by means of NoPhosphate.
Note: although the results obtained confirmed what Wilkens stated, the fact that the coral detached from its skeleton does not mean that this would be the case for all corals. Only that Lobophyllia was obviously sensitive to the presence of phosphate and was adversely affected by it.
Because of our move from Las Cruces to Atlanta, I have not been able to perform this test on other corals yet to determine if the same would happen. I encourage anyone who is into research to investigate this further though as confirmation that such happens on a more generalized basis will give us yet another edge in improving our water quality and the environment for corals and prevent receding and polyp detachment.
The next page shows the results of the testing:
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