Emerald died, unsure why

[Kooma]

Hey all, A couple weeks ago I grabbed two emeralds for my cube, I have had a decent bubble algae outbreak that went unchecked for many years while priorities were elsewhere. I noted both in there a day or two later, then only noted 1 with no sign of the second. This went on for about a month now, and yesterday I noticed the one that did come out sitting on the top rock lights on not moving. I was in a rush and noted it for tonight, but my wife called telling me my clowns were playing with it and she thought they killed it. It was on the sand upright when I found it tonight. I netted it, it was not moving but also wasnt "stiff". Nothing has changed in the tank in the past two weeks other than dosing Mag to bring it up from around 1050. Calc was 450, nitrates are around 25, 77.8F and 1.023. The tank has been running happily with the clowns for 6 years now. Ive never had much luck with emeralds and even though they did a fantastic job of the bubble algae, I cant seem to make them last. Worth noting that they didnt run out of food, there was still a fair bit to eat, but my rocks looked much better.

Tank has 2 clowns, a nem, some coral frags, a scarlet hermit, urchin and two snails.

Any suggestions I should check for?

Dosing with Seachem Mag, I mix 25 grams dry in RODI water and dose nightly as i try to bring up my magnesium. All corals look happy, nem looks great, clowns are unaffected as are the rest of the CUC.

The crab looked perfect other than it was completely limp.

 

[Nano_Tuners]

Probably starvation. A lot of crabs in tanks die from starvation

They may not automatically go for the diet (nuisance algae) you hope they would

 

[Kooma]

Probably starvation. A lot of crabs in tanks die from starvation

They may not automatically go for the diet (nuisance algae) you hope they would

I was thinking of that, but they cleared a massive amount and there was still more to go. Would they swap diets and choose to starve over continuing on bubble?

 

[saltienewb]

Crabs are fickle imo. I’ve had some last years and some last months. They’ve been working for you so I doubt it was acclimation, but there is no way to know, especially if your other inverts are still alive

 

[Nano_Tuners]

I was thinking of that, but they cleared a massive amount and there was still more to go. Would they swap diets and choose to starve over continuing on bubble?

I’ve had a band of scarlets start dying when there was algae around. It seemed that once they got a taste for leftover fish food they’d rather die than eat algae

They’ve almost all died off now and I’m gonna stick to snails. An urchin would be a good suggestion for battling lots of algae

 

[Kooma]

I added a pin cushion urchin last week that's been obliterating the GHA on the back wall. Never see it so clean.

Thanks for the info. Ill avoid them moving forward. Unfortunately, they are one of my sons favorites....