I found this information
www.kentmarine.com/faqs/saltwater.html
Q: My calcium will not go above 200 parts per million. How can I raise it up?
A: Check your alkalinity(carbonate hardness or kH, etc.) to make sure it is not too high. Reef tanks should not exceed 10 dkh. A high alkalinity can cause the calcium level to fall. Check your magnesium level. Magnesium plays an important role in keeping calcium in solution. Usually a high quality brand of salt will provide the proper concentrations. You can also supplement with Tech•M magnesium additive to attain the desired level. Use Kalkwasser as a steady drip to replace evaporation. Also use Turbo-Calcium or Liquid Calcium, to elevate the reading to 400 + ppm or use new Tech•CB.
Q: I have a red slime covering my rocks. Is there any way to get rid of it without harming the delicate corals?
A: "Slime algae" (which is actually a cyanobacteria) come in different colors, such as blue-green, red, brown, and black. They primarily live off of organic materials that have built up in the aquarium. Some organics are not removed by protein skimming. Poly-Ox will oxidize these free organics thus cutting off the food supply. Do a small water change prior to treatment and remove as much of the algae as possible. Poly Ox can also be "painted" directly on the slime outside the tank for quick results. Then rinse with salt water.
Q: All my soft corals are closed up, what can I do to make them open?
A: Check your lighting and aquarium parameters. Start using a good iodine supplement. Iodine is removed very quickly in the filtration process. Use Tech•I or Concentrated Iodine for this addition.
Q: What is the difference between SuperBuffer dKH, and Marine Aquarium pH Buffer?
A: SuperBuffer dKH is recommended for reef tanks. Marine Aquarium Buffer is designed for fish only aquariums, and maintains slightly higher pH.
Q: I use Essential Elements in my reef tank, do I need to use Coral-Vite as well?
A: Coral-Vite and Essential Elements are not the same. Essential Elements replaces trace minerals used up by the animals, through protein skimming, and carbon and resin filtration. Coral-Vite replaces those vitamins and minerals that corals use heavily. Fish only tanks need Essential Elements. Reef tanks need both.
Q: Which calcium supplement should I use in my reef tank?
A: Choosing a calcium is really dependent on how big your aquarium is, and your personal preference. We recommend using a Kalkwasser drip to replace evaporation, and Turbo-Calcium or Liquid Calcium to reach desired levels. Kalkwasser may be more work, but will yield maximum results. Turbo-Calcium should be used by anyone competent in mixing and dosing this strong calcium. Liquid Calcium is recommended for the novice reef keeper or someone who needs the convenience of not having to mix chemicals. Our new Tech•CB calcium buffer system can be used in place of a calcium and a buffer, and may give improved results.