I completely agree with Michael that you should raise your calcium around 450ppm. Any lower than 400ppm, calcification will be extremely slow and may stunt the growth of the scleractinians. You may want to try a two part additive to raise the calcium level. With some Trial and Error when I first started, 20ml of a two part additive will raise the Calcium Aproximently 10ppm-20ppm. I would dose around 20ml of a Calcium Buffer every 24hrs until you acheive a calcium level of around 450ppm. Regular dosings of Kalkwasser (also known as Calcium Hydroxide or Limewater) should help keep the calcium and alkalinity both stable.
i wondering should i expect anything out of the sps colonies?
With 500wts of power compact, you should expect some slow growth and mild coloration from both the M. Capricornis and Encursting Montipora. Montipora is generally quite hardy, and may
live in your tank. If you get lucky, they may show good coloration and good growth, but the chances are slim without halides (but possible).
also if the have bright colors on the tips its certain that they will turn dark brown with an increase of zoo symbiotic algae in them (cant remember how to spell it) LOL
Zooxanthellae- Pronounced "Zoo-Zan-Thell-E"
i just stopped running a po4 sponge.
Is there phosphate present in the aquarium? Phosphate will stunt the calcification process in calcareous algaes and corals (all Scleractinians, including both Large and Small polyped scleractinians, for short "LPS and SPS"). If there is phosphate, continue to run the phosphate sponge until phosphate is gone. Also check to find the source of the phosphate; Top off water, water change water, etc.
If you are planning on keeping them in your current tank under the PC lighting then make sure you have them in the path of really good indirect flow.
SPS corals don't touch phyto as they are carnivourus.
You hit the nail on the head with those two. Good strong current is essential for keeping SPS corals.
By the way Mark- I received your email. I'm waiting until I get a good picture of the coral frags before I email you back with them.
Take Care,
Graham