Euphyllia and pocillapora not doing well

[danamite]

Hello all,

I am attempting to run a 250 gallon coral culture tank and am having some issues. First, the euphyllia do not seem to be doing well (not sure if that green sponge is to blame). Secondly, our pocillapora seem to be bleaching. However, our stylophora, hydnaphora, and montipora seem to be thriving.

We have about 15 hermit crabs, about 150 assorted snails, a couple other small inverts from the fiji live rock, and no fish. The tank is now almost a year old (after live rock was put in).

Our nutrients are all very, very low (about 0) and Alk is a little a little low, but close to target.

Any advise or suggestions would be very much appreciated. I will try to answer any questions as quickly as possible.

Thanks.

[Mark9]

What kind of lights are those, and what are your numbers for ca, kh & mg?

[mcgyvr]

Got a par meter? Lights look really bright from here (impossible to really say that over the internet obviously)..

"very/very low nutrients" isn't a "good" thing to have either.. Corals need nutrients..

I think quite a few are actually over lighting their tanks leading to issues too..

[danamite]

Thank you for replying.

We have the Hamilton Technology 5 ft Cebu Sun Systems - 3 x 400 Watt metal halides and 5 T5 High Output (HO) Fluorescent bars.

We tried to take some PAR readings and got 450 in the center and 350 in the corners of the grate. (units: umol s^-1 m^-1 = uE s^-1 m^-1)

The main tank is 5' by 3' by 2' with the light about 14" above the tank.

As for the low nutrients, I was under the impression that they thrived in nutrient dead zones. As most coral reefs have very low nitrogen and phosphorous.

I'm afraid I do not know the Calcium, Carbonate Hardness, or the Magnesium of the water. I will have to find those out and get back to you in a couple days.

Our total Alk is about 2100 umol/kg

[Radioheadx14]

You water might be too clean for these. They tend to like to have richer water. I add nitrates to my tank for this very reason. I always have 0ppm NO3 and PO4. I am shooting for 5ppm no3 and .02 ppm PO4
I would also look into monitoring and maintaining your alk as some corals do not like Alk swings.