T. Derasa Clam Is Dark??????

[dark horge]

Hi

Actually, most T.derasa I've come across are predominantly blue, with darker markings an/or clear portions to relieve the monotony of the mantle.

It is found on both loose sustrate and penned-in hardbottom, so I'm not sure why people say moving it up the rockwork is bad.

Most failures in husbanding Tridacnids seem to stem from malnutrition (lighting is not enough, and in-tank biodiversity to provide planktonic/detrital nutrition is important), predation (lots of gastropods and crustaceans can have the hots for clam), and inappropriate water chemistry.

I've seen such clams thriving in both bright and less-than-spectacular light --the clam can compensate for less light by consuming more suspended food (if you allow it the option --and no clam can get by on aquarium light alone.).

Your best clue to clam health is comport and growth: If it is proudly expanding, good. If not, then something is ticking it off. Occasional contraction of the mantle can reveal to the sharp-eyed hobbyist the growing edge of the shell, and any evidence of growth.


hth,
horge

[bill-e]

All of what horge said is correct (not suprising). I had a discussion with Daniel Knop about the Derasa and he suggests keeping them off the sand because their gills clog easily. If he's small enough you can very slowly raise him...the problem being that once they get mature, they (any of the Tridacnids) cant adjust to new lighting conditions readily (Photo Adaptation) and can even expire within days of changing those conditions. Having said that, a 3.5" clam should be fine. DT's or cryopaste is a must on a daily basis for best results.

Horge, in the US, most of the Derasas we see here are green and brown...hardly ever blue.

[dark horge]

Bill,

Indeedy, and I also noticed most of your commercially-available Acropora colonies are funky shades of green, blue and pink. In other words, you get what some consider the cream of the crop

horge

[DennisW]

I have about a 3 1/2" Derasa clam on the bottom of my 100g tank located about 22" or so under a 175W True10K MH bulb. It appears dark blue. It dosent appear to have the yellow or org. areas common to these clams. I understand that putting it up higher on the rocks is a no no for this species and that they prefer the sandbed. Any ideas? Or, is this all perfectly normal and fine?????

Dennis

[dark horge]

While we're at it, Daniel Knop seems to have felt at one point that T. derasa is not, err, significantly into filter-feeding:

"T. derasa is also a "clear water clam" that does not filter anything. It has, in fact very sensitive gills that tend to clog when there is a high density of floating particles in the water, may this be planctonic food or just stirred up sediments from the gravel."
(Daniel Knop, Reef-L List, 12/5/99)

He may have since modified his position, or maybe he was oversimplifying in the old statement above (common enough for the typing-weary).

He does qualify, a few sentences afterwards:

"But in any case of feeding it should not be done directly to the clam, but only into the whole tank system."
(Daniel Knop, Reef-L List, 12/5/99)


We do agree on observations of the prevalence of hardbottom or large-aggregate situations for T. derasa. Probably he too wonders why a fine-aggregate situation is so often recommended for the clam.