I have a large 10 inch Derasa that I got some months ago. Recently, the clam has been retracting more and more during the lighting period, to where I'm able to see the white shell in the interior. However, at night, the clam looks fine, closed a bit, mantle slightly over the edge, siphon extended out in feeding mode. Because of the size, the mantle sits midway in the tank, likely getting a solid 300-400 PAR. Could this be a reaction to too much light? It's weird, because I hear that clams can acclimate to any level of lighting.
Derasa too much light?
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B0brobert
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There is a good article on clams and light : https://www.advancedaquarist.com/2011/3/inverts
What does the clam look like when lights go on for the 1st hour? Can you get pics of when lights go on and how it looks when lights off?
Pulling back to see the inside of shell is a reason for concern, they can just close up generally, however if it's a big guy it might not be able to fully shut and could be getting damage.
Can you shade it at all?
Pulling back to see the inside of shell is a reason for concern, they can just close up generally, however if it's a big guy it might not be able to fully shut and could be getting damage.
Can you shade it at all?
I've done a PAR measurement. Close to 400 PAR all over the mantle. The only area of reasonably low PAR is at the very side of the tank, about 150-200 PAR. I've moved it to that area, and it seems to have a bit more extension, but we will have to see how it reacts.
I've tried to orient it differently, and the mantle does not flap, despite the very high flow in the tank. There is no mantle curling, and coming from Biota, I expect the clam to be decently healthy. Unlikely that there are snails for this reason, but I did not see any upon checking the underside. None of the fish bug the clam, except for a chalk bass that likes to lay on it, but I don't know if that is the cause of the retraction. I've moved the fish to another friend's tank for the time being in case.
I've tried to orient it differently, and the mantle does not flap, despite the very high flow in the tank. There is no mantle curling, and coming from Biota, I expect the clam to be decently healthy. Unlikely that there are snails for this reason, but I did not see any upon checking the underside. None of the fish bug the clam, except for a chalk bass that likes to lay on it, but I don't know if that is the cause of the retraction. I've moved the fish to another friend's tank for the time being in case.
If getting too much light I would expect it to fully open in the morning, then gradually retract as the photoperiod is extended. Sounds like this clam is directly from Biota and not a hobby tank? I would shoot them and the vendor (Guessing DD?) an email or call and ask what lighting it was kept at not at DD but at biota. If it's a 10 inch think of how much surface area is getting 400 par with that huge mantle extended, that is a lot of light! How long is the photoperiod? A lot of places raise these clams outside with shade cloth which varies a lot depending how thick the cloth is, but I would guess they don't get that much daily light as your clam is getting.
I missed the part where you said that you have had it a few months already. This has been progressing then? You said recently it started pulling in so it appeared to be fine several months under the same lighting?
Did the shell have a white growth margin on the edge when you got it?
I missed the part where you said that you have had it a few months already. This has been progressing then? You said recently it started pulling in so it appeared to be fine several months under the same lighting?
Did the shell have a white growth margin on the edge when you got it?
Well, when I first got it, it extended as usual for a few days, then the mantle did not open nearly as much (perhaps an inch from the edge) for about a month or so. Then progressively, it has shrunken back to what it is now. There is no gaping of the mouth, and the clam still is able to push a massive amount of water as it closes, so it seems strong.
The shell did have a small white margin when I got it. As I look at it now, the inside is still pearly white, so I don't exactly think that there isn't enough light for growth. I have not seen an increase in the shell margin though, but I don't think large clams grow as fast either. My thinking now is that if it's not the light, I wonder if I don't have enough nutrients in the tank? I was dosing Vibrant at this time too, and my nitrates were too low to even support chaeto. I've stopped Vibrant for a few weeks now, but I run both carbon and Purigen to keep the water clear. Notably, the skimmer has been barely outputting anything from the addition of the carbon. I've removed the carbon for now, for the water is pretty much crystal clear.
With a clam of this size, I'm sure it filters a lot from the water column, but I don't exactly know how much NO3 and the like that it consumes daily. I've incorporated sodium nitrate dosing to get my NO3 above 0 (indicated by my API kit) and will see if this affects the clam at all.
I have a Hippopus and a small blue squammy on the sand, and they don't seem phased by my current water chem. The Hippopus is actually starting to show a slight bit of retraction though.
I know that I'm not gonna find the cause if I change so many different things, but I want to do all that I can to save the clam, it was not cheap, and it's out of the guarantee period.
The lack of nutrients sounds reasonable. How much do you feed the tank daily?
I wasn't questioning if there wasn't enough light for growth, just if it's not happy they will not grow and most really big clams ime have even a tiny amount of growth is all.
I would try and maintain detectable nitrates and phosphates. Supplemental feeding might also be a good idea, phyto seems warranted.
I wasn't questioning if there wasn't enough light for growth, just if it's not happy they will not grow and most really big clams ime have even a tiny amount of growth is all.
I would try and maintain detectable nitrates and phosphates. Supplemental feeding might also be a good idea, phyto seems warranted.
campaign000
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Same thing happened to my friend who has a 16" derasa. He observed no nipping from fish, but the mantle extended better after he insulated all fishes.
Why the mantle extended more in the night? Not only the lights off but also fishes went to sleep.
You can't keep eyes on fish every second.
Why the mantle extended more in the night? Not only the lights off but also fishes went to sleep.
You can't keep eyes on fish every second.
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I have long suspected fish kill more clams than we know. I have personally seen "clam safe" fish nip mantles like purple and kole tangs, had to set a time lapse phone to see it. Doesn't take much to do harm.
Hmm, I just caught my dusky wrasse taking a swipe at the mantle, my tomini also likes to take a swipe at the slime on the clam. I don't see any bite marks though. I don't know why they're targeting the derasa in particular, my squammy has never had that happen to it. I just realized that my auto feeder has not been working properly, not putting the right amount of food in the tank. I feed mysis once a day otherwise.
Here are some pics:
As it looked a month ago
How it looks now. I know, not pretty.
Close-ups of the retraction. That portion does look particularly slimy.
My other clams. Ignore that retracted part on the squammy, I accidentally broke a part of the shell and the mantle is trying to regrow it on that portion.
Close-up of the retraction on the Hippopus. Slight, but noticeable.
Here are some pics:
As it looked a month ago
How it looks now. I know, not pretty.
Close-ups of the retraction. That portion does look particularly slimy.
My other clams. Ignore that retracted part on the squammy, I accidentally broke a part of the shell and the mantle is trying to regrow it on that portion.
Close-up of the retraction on the Hippopus. Slight, but noticeable.
B0brobert
Community Member
I had to put a net around my Maxima because my hippo tang nipped it and was closing all the time.
I would bet those two fish are the culprit. It doesn't take bite marks, just extended retraction and once the fish thought happens that irritation = delicious slime you can't break that habit that I found at least.
It might be the fish are nipping related to the declining condition too.
The hippo is concerning too.
It might be the fish are nipping related to the declining condition too.
The hippo is concerning too.
Huskymaniac
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Not gonna sugar coat it but that clam doesnt look good. Very similar to hiw mine looked nefore it died. It took a while to get to that point also. I would try moving it to another area and see what happens. It came from DD correct?
I'd have used a gentler method if I could, but with sand and rock, there is no way to net a wrasse out of there. The Dusky is now in the fuge, no shortage of pods there to eat, so he will be fine. If the tang is not a horrible offender, I'll keep it in the DT. Let's see how it goes.
Fingers crossed not too late! Big guy like that might bounce back quickly once is no longer pestered. Just keep eye on other fish too!
Edit: wow that was fast! Nice job. I have used barbless hooks too, I think overall it's less stress than tearing apart the tank and chasing them for an hour.
