Fishes died after substrate disturbed

[rainmalawi]

I started my marine tank in Jan 2013. My reef tank is 4 x 2 x 2.5. Recently one new fish has died and found lodged under a pile of rockscape. As it was lodged under a large piece of base rock and was not visible from the top of the tank, I need to use a long object to "dig" blindly for it. I spent a good 15 minutes trying to retrieve the body and the base sand (very fine type) has been disturbed at the localize area due to the digging. After this, my most hardy fishes and fishes that has been with me since Jan 2013 started to die off one by one in a span of 3 days.

1. Fire goby - have it since Jan 2013

2. Large blenny - have it since Jan 2013

3. Large yellow wrasse - have it since Jan 2013

4. Large orange tail blue damsel - have it since Sep 2013

5. Azure damsel - have it since Sep 2013

6. Falco hawkfish - have it since Sep 2013

All the above fishes are healthy and feeding very well. My water parameters and daily routine has not changed. The body of the fishes have no visible injury, disease and looks perfectly well. I have observed the fishes displaying fast gill movement, lying on its sides, darting around blindly before death.

Anyone with the above experience can share.

Thanks for reading.

[Snoopyhamburger]

This is probably due to ich,if I can recall.Read about this a year ago before I started my tank so...

The ich reproduced and the cytys

(Is That What It's Called?)

fell onto either the rocks or sand,ready to continue the life cycle,if it can catch a fish. XD

In this case,you stirred up the sand and the offsprings clung onto that new fish and that is what may have caused its demise.

Pls don't say mean things,I had a really hard time recalling this.

[I love angel]

May due to ich as mentioned by snoopyhamburger or ammonia spike.

[vidextreme]

That's definitely Hydrogen sulfide poisoning. Hydrogen sulfide, is a natural accurance in a tank, unfortunately and it's part of the sulfur cycle in a tank. This is why tank needs sand sifters and live rock cleaners (snails, starfish, etc)

Hydrogen sulfide is poisonous even for us humans. It occurs with decaying matter got trap in a anaraerobic environment, meaning no oxygen. Say, dead fish under the sand.

Typically, hydrogen sulfate is released in safe amount in a working tank with sifters. You can tell by looking at the rocks or sands with black tint in color (metal form). They are eventually released in a form of gas and go out of the tank this way.

Without sifters in the sand, hydrogen sulfide accumulate. And they can kill anything in the tank once released in dangerous levels. This is why, snails and chemical filtration are essential tank components. This can also be complemented with a good water circulation in the tank.

Some readups http://reefkeeping.com/issues/2005-12/rhf/

[blusafe]

Ich burying into sand is a ridiculous concept...I haven't seen anything scientific supporting that assumption! The longest known marine ich cyst hatched after 72 days. So in this situation, if it was ich, then all the fish should have had a low infestation level until death. Ich is not a "sudden" killer. The fish should have many white spots before slowly succumbing to weakness and secondary infection. Not in three short days. The OP would definitely have noticed if ich killed the fish.

I second the toxic gas hypothesis, probably hydrogen sulfide. Should notice a rotten egg smell. Enough H2S can kill an adult human with a single breath.