Why aren't my corals growing?

[Zirco]

I've had a these frags in my tank now for about three months and they aren't doing as well as I expected, particularly with respect to growth.

Green hairy mushroom coral (steady but not growing)
Leather toadstool (grown a tiny bit)
Rhodactis mushroom (steady but not growing)
Venus fly trap palythoa (steady but not growing)
Florida ricordea (maybe grown a tiny bit)
Zoanthid (steady but not growing)
Birdsnest (in decline)
Pocillapora (lost color but still has polyp extension)
Pink Cap Montipora (still pink but hasn't grown at all)
Green Psammocora (lost some color, hasn't grown but looks OK)

Suspecting my lighting, I recently bought a Seneye to measure PAR in the tank. It was indeed much lower than the BuildMyLED specs led me to expect. Directly under the lights I'm getting about 220 PAR and at the bottom of my tank about 70. I have the controllable 20K lights they used to sell and they are hung about 8 inches above the tank.

Water params:
Nitrate 0
Phosphate 0
Alk 9.1 dkH
Calcium 390
Magnesium 1350
pH between 8.15 and 8.28
temp between 77.5 and 78.0

Am I right that I need more light?

[thegrun]

A little more light would certainly help, but some of your corals do well in low light so lighting isn't your only issue. What is your lighting schedule? Your calcium is a little low, I would bring it up to around 430. You don't list your salinity, be sure it is close to 1.026. Stability is the key with corals, if you are dosing many small doses are preferred to a single large dose when the water chemistry changes are bigger.

[Percula9]

Try lowering your lights to 6 inches above the water.Bring some of your corals closer to the light.

[Zirco]

A little more light would certainly help, but some of your corals do well in low light so lighting isn't your only issue. What is your lighting schedule? Your calcium is a little low, I would bring it up to around 430. You don't list your salinity, be sure it is close to 1.026. Stability is the key with corals, if you are dosing many small doses are preferred to a single large dose when the water chemistry changes are bigger.

I've been keeping my salinity at 1.025. Dosing alk, calc and magn by hand every day. Surprised how much I need to dose given that I just have a few small frags.

Try lowering your lights to 6 inches above the water.Bring some of your corals closer to the light.

I've moved the corals as high as I can for now. I stupidly cut the wires that hang the lights so that there's no slack for easily lowering the fixture.

Part of the reason I'm asking about this is that I'm considering buying a slightly used Pacific Sun hybrid LED/T5 (http://www.pacific-sun.eu/new/index.php?option=com_content&view=article&id=89&Itemid=189) that someone in my club is selling.