[Uel]

I have a Blue Dot squamosa that is bleaching in the center. I have checked for predators and the water is fine. I have had the clam since 4-5-02. It has added four shutes of growth since then and is 7-8 inches long. The mantle is fully opened. I will post a link to a pic.

[Uel]

Here is a picture: http://community.webshots.com/photo/...61944738iZZtUg
Thanks in advance.

[Barry N.]

Uel, Welcome to Reef Land.

Looks like central bleaching to me. It is caused by loss of symbiotic algae. Some people thinking is a deficiency of a spectre in the light source. ( Braley1962)

This could be caused by the clam not producing pigments to shield it from the ultra violet lights. Sometimes this can happen when a clam is kept under insufficient lighting then intoduced to a much brighter light. One reason why care should be taken when acclimating clams to new lighting. This can be done IME with a shield placed on top of the tank and slowly removed over a few weeks. Normally once this starts there is not much you can do, you can slowly give it more light but in most cases reported it will slow it down but not stop the bleaching.

Barry

[Peabody]

My understanding is that it can be caused to to lack of nitrogen foods (No nitrates can be bad for clams!) and also due to lack of light.

What lights is he under, and how far is he from them? Also, what are your nitrate readings?

Best of luck
Jeff

[Peabody]

OK, Barry beat me to it! I forgot about the UV thing.

I don't seem to be able to edit my posts, but I meant to say No nitrates CAN be bad for clams.

[kevinpo]

Jeff,
There you go

I've had my clams get light areas on the mantle but not white like your picture. Mine recover their color slowly over time.

Kevin

[Uel]

I have 2 - 250w 10,000k MH's and 96w of pc atinic on a 180gallon tank. The clam is on the bottom directly under the one of the MH bulbs, which is 6" above the water. It is roughly 20" from the light. The clam has been in this spot since the middle of April '02.

Barry, are you saying I should move it to more light? The bleaching has just showed up in the last week, before that it looked good. You can see some older pictures at http://community.webshots.com/photo/...47430891oVWlBz
That picture was taken in August '02.

My nitrates hover around 10 - 20 and sometimes 30, but I won't let it get above 30. alk-12, cal-400-450, am & trites- 0, ph 8.0-8.3 (I have a probe in my tank and cal reactor), salinity - 1.024. I use kent phytoplex 3-4 times weekly. I dose iodine and strontium weekly.
Thanks guys.

[Ninong]

Hi Uel,

Your lighting seems just fine considering the placement of the clam. So I don't think your lighting could be the problem even though that is always the number one suspect in central bleaching. Braley thinks it is caused by a lack of the correct spectrum but Knop disagrees with that and thinks that it is caused by either too much UV radiation or a sudden change in UV radiation.

In your case, unless you experienced a recent change in lighting, I just can't see how your lighting could be the problem. In any case, I would not move it into higher lighting. If you want to play with the lighting, just reduce the photo period by an hour or two daily and see if that helps but it may be too late to reverse the condition.

Something has caused the clam to lose its zooxanthellae in the center of the mantle and since that is the area exposed to the most intense light, light is always the number one suspect, but I wonder if the problem could lie elsewhere. Why are your nitrates 10-20 ppm (and sometimes 30 ppm) with an Aqua-Medic 1000? How often do you have to change the stuff that goes inside the denitrification chamber? What about the mechanical filter, do you clean that out frequently? I realize that clams like nitrates but Daniel Knop says that the ideal nitrate reading for clams is 1-2 ppm. Your pH is fine and your alk and calcium readings are excellent, but I think you should consider raising your specific gravity to 1.025 or 1.026. Here is an interesting article on specific gravity (salinity): http://www.animalnetwork.com/fish2/a.../1/default.asp

Have you ever tested your iodine/iodide levels? I see that you are dosing on a regular basis but are you sure that you haven't overdone it in that area? Iodine can be extremely dangerous if overdone. It is the opinion of Dr. Ron Shimek that the common foods that we feed our reeftanks already contain sufficient iodine -- something to consider. Here is a link to his article: http://www.animalnetwork.com/fish/data/foods.asp

[popcorn]

Would the spectrum shift resulting from aging MH bulbs do that? I'm beginning to notice some speckling on the mantle of my derasa, and I know we're overdue for new bulbs...

Danielle

PS. Anybody got a hellolights.com coupon?

[Barry N.]

A sudden increase of lighting which results in more UV-rays can cause the bleaching process. When changing your lighting from old to new, the acclimation period should start again. In your case I do not know when you changed your lighting?

If the clam does not have sufficient pigmentation to shield it from UV the symbiotic algae will slowly die.

Knop states:

A sudden increase in the amount of UV light, which could still be in a physiological range. This could be caused by keeping the animal under low light intensity with a sudden rise, not alllowing the animal to adapt to the new conditions.

He also go on to say that this can be compared to the tanning of the human skin. A moderate exposure to sunlight can trigger the production of a pigment in the skin which shields genetic information in the cells against damage by further UV-ray. The amount of pigments produced is always in accordance with amount required for protection without impairing certain biochemical processes. If the skin is exposed to a sudden amount of UV light, sunburn will be the result. A long term exposure may lead to a cancer of the skin. He beleives that this may be similar in the Tridacnid clam.

I have never seen a case where central bleaching will heal itself, you may slow it down with increase lighting over a period of time but once the symbiotic algae is dead, my understanding is that it will not come back.

Not good new but that is my experence. If you wouldn't mind, track the spread if any and keep us posted,

Barry

[Uel]

Thanks guys.

Barry I did clean a cover on my lights and this did increase the brightness. I cut an hour off the photo period, but it was obviously not enough. I have the aquascape lights that are enclosed, the glass had a white (hard) film on the outside. I scraped it off for the first time in several months about three weeks prior to my 1st post. I will have to make checking this a monthly thing.

I have noticed a few brown spots beginning to appear in the bleached area. I purchased some Instant-Algae from Jim Norris and he asked if I would feed the clam every other day, in a bucket for 30 minutes, to see if that would help. I just put it in an old salt bucket with 2 gallons of tank water and four drops of the algae. I will keep you posted on any results.

Luckily none of my other clams were affected in a harmful manner by the change in lighting.

Thanks again for you responses.

Uel