Just want to add my experience with T5 and Crocea Clams. I switched out my dual 150W DE MH lights 2 months ago and replaced it with a nice 5x39W T5 fixture in my 38G tank. I first lost my oldest (approx 6 years) Vietnam Crocea a couple of weeks ago. This week, I lost both of my Ultra Clams (approx 4 years). So sad. Not much has changed in the past 2 months in my tank other than the lighting. All other livestock are well and thriving.

I have a Tek 6x54W and a crocea clam. The color has faded a bit but the clam is doing good. I've had it for 6 months now. Just changed my bulbs so I'm curious to see what happens to the coloring.

I keep a Crocea 24" deep in my tank. He has been in there for a couple months now with no issues.

Lighting is as follows 4-24W T5HO 2 KZ Fiji Purple, 1 Blue+, 1 ATI White Actinic. I would like to add another 10K and remove one of the Purples.

I have clams in my 30 gal with 4xT5. So far they seem content...well opened with good mantle exposure. I had one in my tank with halides and it shrunk away to nothing..there are aptaisia in the tank and I wondered if they irritated it. Anyway when I got others I put them in the T5 tank. What are early signs of them not thriving? If they decline I could move them to the halide tank.
I agree that success is based on the test of time and 5 months isn't much time:( They are laying down new rings of shell so I hope that is a good thing.

10 clams....maxima,crocea and derasa...... 2 36" 6 bulb teks over a 72" tank. I dont think my clams look at all unhealthy.....

When looking after Mike,s old 120 with an 8 bulb fixture, I noticed the clams needed to be higher up to look good. Seemed to lack light on the bottom, which would have been about 30in. from the light hood.

Same in my 90g with a cheaper 6 bulb fixture. In both cases, clams like derasa & squamosa were fine on or near the bottom but not crocea or maxima,s