Bleaching hermit crab shells, coralline algae

[Claw Atticas]

I just bought 30 Blue Leg Hermits (Some turned out to be Red Legs, but I'm not complaining), and I noticed about a day after I put them in my tank, some of their shells started bleaching. There's also a small amount of white spots on the coralline algae in my tank (Though there is a big section of bleaching around the downward-current flowing from the fuge to the tank). I have a Nova Extreme T-5 with moon lights, 2 420nm Blue Actinics, and 2 12000K White Actinics, and I haven't changed the bulbs since I bought it around April of last year (Even though they seem to work alright) Current water parameters are Calcium 400 pH 8.3 Ammonia 0 Nitrites 0 Nitrates 5 Phosphates .25 Have a large Xenia coral 'forest', and a little bit of Galaxea coral (Also a clownfish and coral beauty angelfish, but that's not important here)

 

[melosu58]

Three things you want to check when it comes to Coralline is Calcium, magnesium and alkalinity.

 

[roka64]

Sounds like the algae on the shells are getting used to the new lighting/parameters. You may be looking at a change in bulbs as well.

 

[Claw Atticas]

Well, it wasn't algae on the hermit crab shells, they were more of a light brownish color, and just turned pure white a day after I put them in the tank.