Dying clams

[rxx2]

Hello, was wondering if anyone has a little advice or insight as to what is going on regarding my dying buddies.
I have a 36 Lx36 W x24 H inches (approx 135 gallon) acrylic tank that has been up and running for 8 months. Have about 2 inches of oolitic sand on the bottom. Gobs of live rock.
Overflow into a sump that holds about 15 gallons, also has a 2 inch sand bed in there that I have frags growing out in.
Return is via #2 Eheim 1060's (one flows through a 1/4 hp in-line chiller) and a Mag 7 through a 1/2 inch SeaSwirl. Also have 6 powerheads in the tank behind the live rock. Skimmer is an Aqua C EV-180 powered by a Mag 9.5 throttled back a bit, does not produce much skimmate. Lighting is via #2 10,000K Hamilton 250 watters, #2 10,000K AB 400 watters and #4 36 inch VHO actinics.
Have a Korallin 1501 hooked up. Have had some trouble getting it dialed in so have been having to dose 2 part calcium.
Hmm, did I forget any other data that would be helpful
SPS, many frags and several colonies are doing well.
Recently I've had 2 clams that look well for about 3 weeks then will start gaping at night. Look fine during the day, react to light, then again gape at night. This will go on for 1-2 weeks until they finally succumb to something, usual course is that at some point in the AM before all the lights come on I'll see a peppermint shrimp tearing the clam apart and will immediately pull it out.
I have 1 fish in there, a Potter's wrasse.
Feed 30ml of DTs daily, brine shrimp about every other day.
use 30ml of Korallin S-Plus every week
Tech-M (magnesium) 20ml q week
SP GR 1.025
alk 3.2 meq/l
Ca++=400
nitrates negative
have not checked ammonia, nitrites, or magnesium
Any thoughts or comments would be greatly appreciated.
Thanks, rxx2

 

[Peabody]

Many clam experts stress that clams need nitrogen, especially nitrates (also a trace of ammonia and nitrite). In fact, many clam farms add nitrate to their systems. WIth one fish and no nitrates, an important clam food is missing. (Probably also why you are getting no skimmate)

Before anything can be determined, you ought to test ammonia and nitrite. If you get a reading on either of those, you might have found your problem.

Also, why are you dosing magnesium?

 

[rxx2]

Thanks very much for the reply.
I read that in Knop's book about the nitrates. I'll check ammonia and nitrites. Perhaps I'll have to add more fish. Do you know where to get sodium nitrate?

Was adding magnesium because a few months back had a problem getting my Ca++ up and had heard that low mag could be the problem. I guess I should test that also.

Thanks, rxx2

 

[Peabody]

In my uneducated opinion, I would guess that the mag. is not a problem, but if it was me, I'd test for anything I dose.

I wouldn't know where to begin on the sodium nitrate thing. If it was me, I'd just get a larger fish bio-load, because you would have to be very careful, and monitor dosing a nitrate source very closely.

 

[rxx2]

Thanks again for the input, rxx2

 

[rxx2]

Got some Salifert test kits, was using the Red Sea ones, just to make sure that I had reliable results. The ammonia, nitrites and nitrates were all ZERO. I guess I'll have to get more fish. I might try to get some sodium nitrate through Sigma-Aldrich then make a stock solution like in Knop's book to see if it'll work.
Also tested Mg++=1290
Thanks again for the input, rxx2

 

[Mad Scientist]

In the meantime, before you get more fish, start feeding with DTs, it will help alot in this case.

 

[Leopardshark]

Another possible cause is that you have an Oenone fungida worm in your tank.
Those are rare worms that come in the live rock, they produce a mucus to cover clams or snail and they suffocate them.
When they are dead, they eat them.
THose worms looks like regular bristle worms but they have an orange color.
HTH
Marco

 

[Turtlesteve]

Leopardshark, can you post a photo because all of my bristleworms are red/orange.

They have never killed anything though...

 

[Leopardshark]

Unfortunately I canÃ"šÃ‚´t because I donÃ"šÃ‚´t have one.
In my tank I had 2 8" worms that probably ate my clam, it was a green Maxima
I would check all the rock in your tank (i know it is a hassle, but I think itÃ"šÃ‚´s worth it. MY tank has 250 lbs), at least you could eliminate a possibility.
They donÃ"šÃ‚´t have to be big to kill snails or clams. Do you remember or noticed if the clam was covered by a cristaline mucus when you took her out of the tank???

 

[Schweb]

If I were you I'de talk to Barry at clams direct .com I just got a beautiful gigas from him. I spent a lot of time talking to him and from what I was able to gather he is a great source of info and clams!