Hardy fish and invert death with no signs or symptoms and decent water quality

[benmorrow1978]

I've got a 75G with 200+ pounds of live rock, mostly covered in coral (star polyps, xenia, etc), a large brain, a recently reproducing frogspawn, a purple sea whip, sea cucumber, numerous blue legs and snails (50+ blue legs I'd say), a clown and a bi-color blenny. All the above are healthly to the best of my knowledge and as mentioned, the frogspawn has recently split and has doubled in size in the last year, I have tiny xenia growing on live rock, the brain has increased 30-50% in size in the last year, everything has been just peachy.

2 months ago, in addition to the above, I had 2 cleaner shrimp (in the tank 8-9 months), a purple fire fish (in the tank 4-5 months) and a mandarin dragonet (in the tank 2-3 months). These all appeared healthy, and the mandarin had been trained on Black Jack Reef Crack.

I normally feed my fish 1-2 times a day. I shoot for two, but occasionally I run late for work. In July, I went on vacation. I didn't feed them for the week, which from what I've read here, is OK. I left the lights off. I came home missing a purple fire fish. No floater, no jumper, nothing. I'm assuming my crabs ate good that day. About 2 weeks later, I lost one of my cleaner shrimp. Again, no symptoms, eating fine the day before, then I wake up to crabs having shrimp for lunch. Last week, lost my other cleaner shrimp. Came home from the lake after a 3 day weekend yesterday to a dead dragonet. Again, no visual symptoms, fish was eating fine on Friday and appeared healthy. My fiance's mother fed them pellets during the weekend, 20 pellets per feeding, 2 feedings a day. She's so scared of hurting anything, she wanted exact instructions!

My water parameters are all good. pH is just a tad low at 8.1, SpGr 1.026, Temp 79, Amm 0, Nitrite 0, Nitrate <20, Alkalinity is a tad high at 5.0 mEq, Calcium could use a boost at 320, and Phosphates <0.2.

I routinely change 10 gallons of H2O per week, occasionally I miss and do a 20G change the following week. I never miss more than 1 week. I was due for a 20G change this weekend, but waited after the discovery of the Mandarin carcass, to see what the experts have to say here.

Again, no physical symptoms, everything appears A-OK, the next thing I know they are gone.

I'm not a careless fishkeeper. I've had this tank for just over a year, and I've lost one fish prior to what you see above.

I have my suspicions, but I want an opinion from someone much smarter than I, without my suggestion. Any ideas? Need more information? I don't have much, I don't spend hundreds per week on test kits, I don't know the magnesium level in my tank. I use Reef Crystals.

Mandarins are disease resistant due to their thick mucus layer, so I've read. I haven't had a massive die off of snails or crabs.


HELP!

[Reefing Madness]

Well, I'll take a stab at the shrimp. Your CA is low, and if they can't molt, they die. Its the weakest that go first, so why you haven't lost any snails or crabs I don't know. Carbs have been known to go after fish while they are in hide sleep mode, if they are not getting enough to eat. And my other answer is, some just die for no apparent reason. We can guess all we want to but in the end, its just nature taking its course. I know the reasoning sucks but I've seen many things pass just for that reason, no matter what I came up with it didnt make sense. So thats my other answer.

[leebca]

Sorry to hear of your losses. I'm sure they have affected you, maybe similarly like it does me to loose a fish. You wonder what went wrong or if it was something that wasn't just done right. I can't provide any definitive answers, but I can provide some possibilities.

Especially with the invertebrates you are caring for, you want to have your water parameters in balance. Not just within their respective ranges, but balanced. This post indicates the proper balance (about 1/3 down the post): What is Water Quality. You'll find that you will need to balance the three: Calcium, Alkalinity, and Magnesium. Since you gave no Magnesium number, I suspect you are not minding that concentration. The post tells you how to slowly bring those three into balance.

Other than the above, there are no particular measurable concerns about water quality from what you've reported.

As the immobile invertebrates go, they can be competitive. Despite what most hobbyists perceive, coral do 'fight' with each other. On the reef, a single type of coral might take up a few dozen square yards. They don't live in harmony with each other. I can't give specifics, since I'm not an expert in immobile invertebrates, but some do release toxins in the water to fend off their competitors (as well as the usual visuals, like sending out singers, etc.). These kinds of poisons may are not detected by the test kits we use. One of the few reasons why the use of chemical filters and skimmers are useful and needed. These toxins may or may not affect the coral competitors but can and sometimes do affect the fishes.

The light was off for a while and I suspect that some of your immobile invertebrates need light to 'feed' and live properly. Still if they were well cared for before, one week without light should not be a problem. You are right about not feeding for a week, however all this depends upon whether or not they were properly nourished and properly fed in the weeks before the fast. In a weakened state, if that is the case here, the marine life is more susceptible to 'off' conditions, including pathogens and toxins in the water.

I'd be concerned about the presence of so many crabs. Fish 'sleep' by usually resting near the bottom of the tank. The Mandarin lives most of its life on the substrate -- all these characteristics put the fish in contact with crabs. I would not have hermit crabs in my aquarium with fishes. Not just a preference, but because these crabs, even the 'best of them' are scavengers -- eating whatever they can get their claws on -- growing large enough to attack nearby fishes. You may want to consider their removal. Here is a good read on this subject as well as the benefits of other clean up crew members:
Cleanup crew article on Reefland:
http://www.reefland.com/rho/0305/medprod3.php

3 articles on snails:
The Grazing Snails, Part I - Turbo, Trochus, Astraea, and Kin by Ronald L. Shimek, Ph.D. - Reefkeeping.com
The Grazing Snails, Part II - Abalones, Limpets and Nerites by Ronald L. Shimek, Ph.D. - Reefkeeping.com
The Grazing Snails, Part III: Conchs, Ceriths, Cowries, and Columbellids by Ronald L. Shimek, Ph.D. - Reefkeeping.com

Nassarius Snails as Scavengers in Reef Aquaria Article
Aquarium Frontiers Library [Click the 'impatient' link.]

What the above amounts to is a few minor undesirables possibly stacking on one another. The likelihood of this is not that great, so don't put too much store in the above -- just be aware of these things.

The shrimp don't have a long lifespan. Some do well in aquaria, others not too well. Your temperature for them is good, providing they were not captured in cool waters. Some are from cooler waters and then, in our tropical aquariums, slowly cook. However, the Mandarin should have a life span of over 10 years in captivity, unless you started with an old/large one.

Much depends on how these marine life forms were collected. If collected using poisons (e.g., cyanide) or other chemicals, their lifespan will be shortened. Also, and pretty much lastly, their lifespan is affected by how they were handled, acclimated, etc. from capture to your display tank.

Beyond the above, there isn't much more I can think of at this time. Sorry for your losses, again.

[benmorrow1978]

You guys went the same way I was thinking. I am always careful to not overfeed. I think in doing so, I've left nothing for my cleanup crews to clean up. I read somewhere, probably on the seller's website, to add 1-2 crabs per gallon of water. In their defense, they are small crabs, most are in shells less than 3/4 of an inch in length. I'm going to start baiting them and catching them, move them to my QT and take them to the LFS for some store credit. I still plan to wait 3 months or so before adding anything else. I'm going to heed Lee's advice on water quality and buy a mag test this evening. Thank you both very much for your expertise and even more importantly, you time!