Bleached Coraline Algae -A Sign Of......?

[DiverDude]

My lights haven't changed and the bleaching has been in the last month (bulbs are only ~4 months old). So it's not a perceived colour change (i.e. lighting) but an actual one.

Water parameters are:
SG 1.025
Alk 2.5
Ca 420
Mg 1075
No2 0
No3 0
pH 8.2

Now...what I didn't tell you was that there are some 'issues' I'm struggling with in the tank right now but I wanted unbiased opinions before I mentioned these. I have a bad HA problem When I bought the setup from another CanReefer, it has this issue and I was forewarned. After about 2 months of having the tank the HA was gone.

In the 6 weeks, it has come back with a vengance.

The tank is doing VERY well; everything is happy, healthy and growing like mad -especially the HA !

About 4 weeks ago, I put a small Sea Hare in there to combat the HA (I had done this the first time around and it worked well). It spent 2 days cruising the glass (never ate a thing) and then disappeared into the rockwork. Despite tearing half the tank apart, I have not been able to find the damned thing.

So.... I suspect that I have elevated PO4 (which I don't have a test kit for) and NO2/NO3 which test at zero but I suspect it's the HA that's consuming it all. All this despite doing 15% water changes ever 3-5 days for the last 3 weeks !!

Now with the coraline bleaching, I think I've got my proof and tonight I plan to pull as much HA as I can from the tank, tear apart all the rock and find that damned sea hare and then do a 50% water change. Oh, and I've got a borrowed 36 watt UV sterilizer on the tank to see if that will help too ! (1 watt per gallon -think it's enough ? )

Anyone think I should take the Bio-Pellets out of my reactor and replace them with Phosban for a while ?