Derasa checkup please

[dansyr]

So I've had this small derasa for a few months now, since early July, and all "seems" well but I'm honestly not very them, more so with maximas /croceas. How does this look to you? Should the mantle be this vertical, rather than laying flat? It has good growth (see photos) but it seems like the body is more recessed in the shell than I expected, and when I was cleaning the other day and gently removing some algae from the old part of the shell, it didn't seem like it was closing itself as tightly as the maxima.

Could it be light limited? Or is this normal? I don't have a PAR meter (anybody in SoCal that would let me borrow one, please let me know!) but for context, I have a maxima placed about 5" above it that is going gangbusters, see comparison photo.

Derasa looking end-on (note height of body vs height of shell)

side view (when purchased it was around the dense lines / just below the current algae line, so it's about 1.5x its original height):


For context, maxima:


Parameters :

salinity: 35ppt
pH: 8.39
Cal: 400-440ppm (420 last checked)
Alk: 8-9 dkh
Mag: 1400ppm

NO3: between 0.1 and 10ppm (manual dosing, 10 last checked, occasionally zeros out and I dose back up)
PO4: between 0 and 0.1 (0.02 last checked)

Tank is a little over a year old.

 

[xjiang7]

They all look very healthy with the amount of new growth on the edge of shell; very impressive for a relatively new tank.

 

[dansyr]

They all look very healthy with the amount of new growth on the edge of shell; very impressive for a relatively new tank.

thanks! this is reassuring

 

[kevgib67]

@OrionN ?

 

[ArachnoJoozt]

Two possible reasons I see for not completely extending:
- The Favia next to it could possible touch and irritate it.
- Zoomed in on the second pic, maybe the long algae on the shell could cause the mantel not to extended fully.

Otherwise your clams look very good! Good luck with them!

 

[Rick's Reviews]

Looks beautiful.. following

 

[dansyr]

Two possible reasons I see for not completely extending:
- The Favia next to it could possible touch and irritate it.
- Zoomed in on the second pic, maybe the long algae on the shell could cause the mantel not to extended fully.

Otherwise your clams look very good! Good luck with them!

Thanks for the feedback! Yeah it scares me how much the derasa likes to snuggle up against that favia. It likes to scoot next to it and just park for weeks, so I gave up trying to move it back to “safety”. Luckily that’s my most peaceful favia, I’ve only seen feeder tentacles, no seeepers, unlike some of the other favia I have.

I was mostly curious with how the body seems to sit deeper in the shell than maximas. Is this normal? I haven’t seen that many end-on photos which has made it a little hard.

 

[Uncle99]

It looks withdrawn a bit to me.
I keep no corals close to mine.
That Favia, I give him more more space, and the Xenia, (I think that what I see, it may waive in the flow and “disturb” the mantle, like when you put your hand between clam and light.
Just a thought.

 

[ArachnoJoozt]

Luckily that’s my most peaceful favia, I’ve only seen feeder tentacles, no seeepers, unlike some of the other favia I have.

That does not mean it's not possible, there could be some sweepers at night when you are not watching.

I was mostly curious with how the body seems to sit deeper in the shell than maximas. Is this normal? I haven’t seen that many end-on photos which has made it a little hard.

I would say this is not quite normal, other pictures I've seen of derasa's show a lot more extension.
The possible causes are easy to test though:
- When you move the clam away from the Favia, does it improve?
- Try to scrub the algae off the shell, does it improve?
- Move it away from any coral

When you do one of these things at a time you can exclude possible causes. Since the clam is showing new growth it is still (for the moment) a healthy clam so you still have time to check what is causing this.

This is one of my derasa's showing full extension. Note: it's really small (2''), and I've had it for one week only, so not a derasa specialist, but have been researching them before purchase.

 

[dansyr]

That does not mean it's not possible, there could be some sweepers at night when you are not watching.

Yeah that's what I mean. I've monitored this tank at different times, I come down and check on the tank at 2am, 4am sometimes. This Favia is really reticent to put out sweeper tentacles (unlike some of my other Favia). More relevant though, this Favia was ~ 3" further away until about late august, and there's been no difference. And, I've never seen the hemisphere-type retraction going on typical of mantle irritation as I've seen in maximas (or even this guy if a wayward Capnella floats into contact with it.

So all of the tests have been done, I'm pretty sure mantle irritation is not much of an issue. No change before/after Favia was moved, or even when strawberry conch plows Favia directly into contact with derasa. So not that. The filamentous algae on the side has been recent, maybe two weeks, since nutrients have been on the lower side and I've had to change my NO3/PO4 dosing and it's not quite dialed in (hence the broader range when I listed parameters). Mantle extension hasn't changed. Again, i don't see mantle extension as a problem. Maybe it was a bad photo because that was towards the end of the day, but look at the side-profile shot, the mantle extends about 0.5-0.75" past the rim.

This is one of my derasa's showing full extension. Note: it's really small (2''), and I've had it for one week only, so not a derasa specialist, but have been researching them before purchase.

See this is my confusion. That's a top-down photo, when I look top-down I get a similar width of opening & presumed extension past the shell based on where I see your fold (and others'). My reason for asking for a check-up is now that my Derasa has swivelled to being end-on to the glass, I notice body depth relative to shell depth, and how the mantle is slanted more upwards more often than not. Do you get what I'm asking? Because it's growing fast so I want to think it's not light limited, but I'm worried the body is undersized relative to shell growth, which seems like a light-related issue.

 

[minus9]

Looks like one of three things to me. Flow, light (possibly too much) and sweepers. I would just move the neighbor further away regardless. There's pretty good growth, so I wouldn't change much. After clams get familiar with their surroundings, they sometimes lose their response to movement or light changes. It's not always a sign of something bad, it's just the clam/animal is comfortable with it's surroundings and doesn't feel stressed by movement/changes. It seems healthy to me, so I wouldn't do too much. Sometimes, it's just how they are. You should check them out in their natural habitat. You would be surprised to see how they are embedded in rock or coral and are as happy and healthy as they can be.

 

[dansyr]

Looks like one of three things to me. Flow, light (possibly too much) and sweepers. I would just move the neighbor further away regardless. There's pretty good growth, so I wouldn't change much. After clams get familiar with their surroundings, they sometimes lose their response to movement or light changes. It's not always a sign of something bad, it's just the clam/animal is comfortable with it's surroundings and doesn't feel stressed by movement/changes. It seems healthy to me, so I wouldn't do too much. Sometimes, it's just how they are.

Thanks! This is exactly the info I was looking for. I'll push the favia back a bit more just in case. All my clams have definitely gotten complacent in the predator-free environment I try to keep

And I'm definitely a big fan of tridacnids in their environment! I have a faraway dream of growing a massive porites/montipora colony with a crocea in it....

I grew up around a bunch of rock types (maximas / croceas) and hippopus and the occasional gigas for more lagoon-y ones. So I have more of an image of what happy / natural maxima look like, but can't remember ever seeing a derasa in the wild. But finding an ORA derasa was a lot easier than finding an ORA hippopus, so here we are! Thanks again

 

[minus9]

Thanks! This is exactly the info I was looking for. I'll push the favia back a bit more just in case. All my clams have definitely gotten complacent in the predator-free environment I try to keep

And I'm definitely a big fan of tridacnids in their environment! I have a faraway dream of growing a massive porites/montipora colony with a crocea in it....

I grew up around a bunch of rock types (maximas / croceas) and hippopus and the occasional gigas for more lagoon-y ones. So I have more of an image of what happy / natural maxima look like, but can't remember ever seeing a derasa in the wild. But finding an ORA derasa was a lot easier than finding an ORA hippopus, so here we are! Thanks again

I've been looking for a hippopus for a long time with no luck. Also, I'm in the valley, so if you ever need any help or have any clam/reef questions, feel free to reach out to me. I'm usually at @GoldenStateCorals on Saturday's.

 

[dansyr]

I've been looking for a hippopus for a long time with no luck. Also, I'm in the valley, so if you ever need any help or have any clam/reef questions, feel free to reach out to me. I'm usually at @GoldenStateCorals on Saturday's.

Awesome, thank you! I will probably take you up on that.

I've heard a lot of good things about Golden State Corals, haven't made it out there yet despite being pretty close (Pasadena). But maybe this weekend is the weekend it happens....