Algae Problems - looking for some help

[IJC]

My tank is growing a dark green algae at an amazing rate in the past week - not just on the glass, it's even covering the macro algae, and even some of my corals.

In addition, my snails have been extremely docile - none of them are up cleaning the glass like usual, and there have been some deaths.

The fish are fine.

Some of the mushroom corals are looking a bit shriveled compared to usual, as is the xenia.

I reduced my photo period about a month or so ago (to about 6.5 hrs), due to heat problems, so this growth is especially strange.

My parameters are as follows:
PH: 8.1
Ammonia: 0.1
Nitrite: ~0.2
Nitrate: >5ppm

My theory is the water I'm using. I've been doing fine with dechlorinized tap water up til now, but maybe there's something in the water this time of year? More silicates?

Anyone have any ideas? or similar problems with tap water in Vancouver right now?

Any help would be awesome.

[MitchM]

Can you give a larger overview of your system?
(age, size, lighting,..etc... what are you feeding, (...and that ammonia reading..what's dying?...))
Unusually docile snails are not a good sign - I would call that an indicator..

Mitch

[IJC]

Like I said, there've been some snail deaths, but that's it.

My system is:
54 gal,
20 gal sump
Lots of live rock in the tank, and additional base rock in the sump
Berlin Turbo skimmer in the sump
250watt iwasaki and two VHO actinics
Laguna 7 main pump, 2 802 powerheads.

1 medium yellow tang
1 small clown
2 chromis
1 6-line wrasse

Quite a few different corals - sps, lps, and softies.

A whole bunch of macro that I can't keep ahead of.

Water changes are monthly, 15 gallons.

[IJC]

I'm feeding mysis, once a day.

The tank has been set up in my place since early dec 03, but I bought it as an established system that had been going for a couple years.

[MitchM]

Does it have an original dsb?

[IJC]

It had a DSB, but I removed the majority of the sand when I got it, leaving about a half inch around the rocks when i put everything back together. I do still see nitrogen bubbles in the sand.

[MitchM]

I'm wondering if it's a cyano problem, not algae, then.
Excess phosphates feeding your macros may be the explanation there, plus dying snails, maybe some ph swings at night, etc.
I'm in Calgary, so I don't know about your local water.
If your temp swings were extreme, that certainly won't help things.
Have you tested your source water for ammonia?

Mitch

[IJC]

No, I haven't tested it for ammonia. The LFS uses the tap water though (aquariums west)- they're the ones who convinced me it would be OK ( I used RO'd for the first month or so). I certainly don't think Aquariums west is the premier saltwater pet store in the lower mainland, but it seems to work for them.

[IJC]

Another thing that might be an identifying factor - after the lights have been on for a few hours, there are bits of the algae floating on the water's surface - inspite of the surface-skimming overflow.

[MitchM]

Your turn-over rate may not be high enough then, which would prevent your skimmer from doing as good a job as it could be.

Mitch