question on lighting for clams

[ahullsb]

I am posting this question on behalf of my roommate. Over the past two days, all 5 of his clams have retracted and one or two look almost dead. He has a few Crocea's, a Maxima, and a Derasa. All look pretty bad. I read the other thread about multiple clams retracting, and we are still trying to get to the bottom of this.

Would lack of light over time cause this? He has them under a 250, but at the bottom of a 24 inch deep tank. I've been telling him a bulb that is too old my cause this? Anyone disagree? And the last question, a few of these are smaller clams, only a couple inches. He hasn't been feeding phyto for awhile. I've heard smaller clams need to be fed more, could that be causing it? Any help or suggestions would be greatly appreciated! I will get him to take some pics and I will post them soon.

 

[skinz78]

Old bulbs may be the cause. We need pic's, tank param's, and a fish and invert stock list.

 

[dp reefer]

I'm Andy's roomate whos having the problems. Heres a pic

You can see that the smaller crocea in the back is developing translucent spots, the two smaller derasas are barely open, but the larger derasa on the far right seems fine.

Tank parameters are all good except that nitrates jumped to about 10 in the last week. I re-arranged my rockwork about two weeks ago so this could be the cause. Fish are 1 blue tang, 1 tri-color fairy, 1 purple firefish, 1 royal gramma, and 1 pearl jawfish. Inverts are blue leg hermits, emerald crabs, astria and turbo snails, and a tuxedo urchin.

Possible causes:

The light- 8 month old ushio 20k may be giving off uv?

Clams are too deep?

Clams seemed to start retracting after adding a koralia that may have been giving too much indirect flow to the clams?

Between not being home and being busy starting school I may not be feeding phyto as much as I should (not for two weeks or so)?

A drastic drop in kh after a water change (got down to almost 5) - this to me is the most likely cause.

I switched to red sea coral pro salt and so far I'm not too happy with it I buffered and it still dropped kh more than instant ocean ever did.

So what do you think is the real culprit or what combination? Thanks for any help or suggestions

 

[dp reefer]

Oh and is it possible that the leather could be bothering the clams? I've only heard that leathers bother sps. The leather used to be across the tank from the clams and now its much closer - I'll move it just to be safe.

 

[skinz78]

Your crocea's should be up on the rocks and that is why the one is bleaching. Your derasa's are fast growers so your cal and alk must be in check. I am guessing all the param changes are the culprit. Get them stable and I bet things would start looking better.