[eses]

I searched for a topic on this and couldn't find it, hope this hasn't already been covered to death.

LFS got in a bunch of tank raised "maxima clams" .. Don't know much about them, I'm assuming that name is enough to give a good description of them. Anyway, they are small, about the diameter of a Pringles lid (but oval, not round.) I have PC light, 128 watts in a 29 gallon (4.4/gal half white/actinic) the lady who has been pretty smart at the LFS says I shouldn't have a problem with one in my system as she is keeping them under VHO with less wattage; and being tank raised they are supposed to have gotten used to lower light.

Any suggestions?

[Ninong]

I don't agree with the lady at the LFS. But rather than post a lengthy explanation here, I think it would be better to guide you in the right direction by linking you to 12 articles by Daniel Knop, an expert of Tridacna clams: http://members.home.net/kevdone/AF/O...alf_Shell.html

That should keep you busy for awhile and provide you with a wealth of reliable information on the husbandry requirements of Tridacnids.

Ninong

[bongobrian]

I don't have a maxima, but I have heard that they are easily kept under lower lighting than what clams like deresas and croceas require. I once asked a guy at my LFS about them and he said the same as what that lady told you. I think you have plenty of lighting (especially for a 30 gal) to keep a maxima.

[Ninong]

Originally posted by bongobrian

I don't have a maxima, but I have heard that they are easily kept under lower lighting than what clams like deresas and croceas require.

This is incorrect information. Tridacna maxima clams require slightly less intense lighting than T. crocea but considerably more intense lighting than T. derasa. Whoever told you that T. derasa clams require more intense lighting than T. maxima clams was mistaken.

I once asked a guy at my LFS about them and he said the same as what that lady told you.

Most of the information coming from most LFS personnel is inadequate and often outright wrong. In this case, it is outright wrong.

I think you have plenty of lighting (especially for a 30 gal) to keep a maxima.

How much light his clam receives is not related in any way to the size of his tank, only to the lighting he employs. What difference does it make to the clam if it is sitting in a 30-gal tank or a 300-gal tank? The only thing that matters to that particular clam is the amount of light incident on the clam's mantle. IMO, 128 watts of PC lighting is inadequate for proper husbandry of T. maxima clams. It would be marginal for the keeping of T. derasa clams.

Ninong

[bongobrian]

I stand corrected about the clams... again, I don't have one and it's just what I have heard from others. However, Isn't it true that lighting intensities are cut by about 4 times for every foot of water depth in the tank? that's the reason why the same lights are more intense on a smaller tank than the same lights on a larger (taller) tank. Maybe I'm wrong about that too.

[kevinpo]

Ninong is correct. I have a 10-12" T. deresa, a T. squamosa 7" and 2 -3" T. croceas. I kept them for a couple of years under 175W MH with 440W of additional VHO's Placed 24" directly under the bulbs and through 18" of water this is about the minimum I would keep these. I now have them under 400W MH with an additional 800W VHO but he water depth is 32" and the light are 8" above that. They extend their mantles much more (almost to the substrate now) and look much happier (happy as a clam as it were). T. squamosa, T. deresa, T. maxima, T. crocea would be the normal order from least to most amount of light requirement and water flow. One other note: small clams require less light but as they grow the require increasing amounts. The above is just my opinion and what has worked for me. Please check other sources IE. Delbeek & Sprung Vol. I.

Regards,
Kevin

[Ninong]

Originally posted by bongobrian

Isn't it true that lighting intensities are cut by about 4 times for every foot of water depth in the tank?

You're on the right track here, but you're misstating it slightly. It's the distance from the light source that is measured, e.g. an animal that is 15" from the light would receive approximately 1/2 the light intensity that it would have received had it been placed 10" from the light, and if you move it to 20" from the light, it would receive approximately 1/4 the intensity that it would have received at 10" from the light. To carry this example further, if you move it to 30" from the light, it would receive 1/8 the intensity of light that it would have received at 10" from the light. (Thanks to the inverse square rule.)

that's the reason why the same lights are more intense on a smaller tank than the same lights on a larger (taller) tank. Maybe I'm wrong about that too.

You're not wrong to state that if the animal is closer to the light because it is placed on the substrate only 15" from the light it will receive more light than if it is placed on the substrate 24" from the light. In other words, a smaller tank would not permit you to place anything 24" from the light unless it is an unusual shape. But it is confusing to equate the so-called watts-per-gallon guidelines with any reasonable advice because watts-per-gallon makes little sense for lots of reasons. Which is why I stated that the only thing that matters is the amount of light incident on the individual animal. If the animal is placed under the center of a 128 watt light fixture 12" from the light in either a 30-gal or a 300-gal tank, it will receive exactly the same amount of light, but in the first case the watts-per-gallon would be 4.3 and in the second case it would be 0.4.

As far as the other information the LFS gave out concerning light adaptation, that is misleading, too. Even though Tridacna clams have the ability to vary the rate of photosynthesis based on their environment, this should not be taken as an excuse to provide an inadequate environment. Besides, when they are young their light requirements are not as high as they are later on because when they are young they get a larger percentage of their nutrition from fltering the water than they do when they are mature. So mature clams have higher light requirements than immature clams. It is also the reason for the very high mortality rates of small clams in the hobby. Many people purchase 1"-2" clams and put them in sterile tanks without adequate nutrition to meet their filtering requirements.

It is still a bad idea to try T. maxima clams under only 128 watts of PC lighting.

Ninong

[eses]

Thanks for the replies, it was pretty much my assumption but I thought I would ask before purchasing. I am against trying something with my fingers crossed hoping it doesn't die, so I will wait until I have a proper setup for handling one.