Fish dying

I originally posted a probable cause in the invertebrates forum thinking a new skunk cleaner had possibly killed 2 fish. Now the whole story. The tank with issues is a 29G biocube HQI. My water params are 0 ammonia 0 nitrites .2 nitrates. Alk 9.2 DKH , 450 Cal, 1250 mag. Salinity is 1.024 as all of my reef tanks are. Temp is 78. This tank is very stable and tested regularly. Water changes are done every 2weeks. I've been in the hobby for years and have had tanks ranging from 300g to 8 G. This tank has been up and running for 5 months with amazing coral growth in a mixed reef from zoanthids to high end sps. I started using a probiotic coral food on a every other day basis several weeks ago. I had 4 healthy fish in this tank for the last 4 months. The fish were in perfect health and schooled together without aggression. A orchid dottyback, helfrichs fire fish, B&W ocellaris clown and a yellow assessor. Last week I lost the dottyback, 2 days later the helfrichs. I purchased a Swales basslet and it died after 2 days. This morning my clown was dead. My assessor and cleaner shrimp remain. I was following the manufacturers instructions on dosing and did notice some nice coral growth. The only thing that has changed in the last 5 months is the addition of this probiotic coral liquid food. My thought is the fact I haven't lost a fish in over 7 years other than a few that have "carpet surfed" that this product has to be the cause. Possibly adding too much "probiotic bacteria" that the tank became oxygen starved and killed the fish. Any thoughts or ideas on this would be much appreciated. I immediately came home tonight, did a water change and stopped the use of this product.

I think your theory sounds plausible but as you know so many variables, temp, voltage, disease, and like you mentioned drop in oxygen, what brand probiotic was it?  

Are they breathing heavy or gasping for air at the top of the water?

There are fish diseases in which it may show no signs such as Mycobacterium marinum, and unless you dissected the fish and know what you are looking for you can not eliminate disease, a multimeter will not detect voltage if what ever may be causing voltage is not causing voltage at that moment you measured it (i.e. the equipment is not in a constant short or not on at the time such as a heater, ato pump, etc.), what was the product brand name maybe that will help people help you, but if you ask 10 reefers if they have had fish die for what seems like no apparent reason and didn't show signs I'm sure 7-8 people would say they have had fish die in this way, hopefully someone else has some thoughts but with the plethora of things we all try to maintain at any given moment in our tanks it could be hard to say for sure what caused a fish death. 

Edited by Bryce - March 11 2014 at 11:32am

Thanks for the replies. Fish at no time were gasping for air that would give the obvious signs of oxygen loss. The product was dosed right before lights out, fish healthy and eating then fish dead the next morning. The tanks flow is excellent. I have had previous problems with coral foods I've tested in the past so I have been doing daily testing to make sure this product was not spiking ammonia and nitrates after dosing like many do. This one did not spike any testable parameter. I don't buy the fish disease theory. These fish had all been together for over 4 months, were in exceptional health and all purchased from different LFS. The only thing that I can pin this on is the addition of this supposedly "completely safe" and can't be "overdosed" product.

What is the stuff you were dosing?

I run a monster skimmer considering the size of the tank a cadlights pls 50 rated for 50 gallons. It's a champ. Being I don't know exactly what the ingredients are in this product and me not using the name of the company as not to damage their reputation. I am looking at any any all possibilities before I blame the product. I do not carbon dose. My water is always pristine except when I add this product it does cloud the tank for a few hours then it's back to crystal clear. After the skimmer I run a media stack by intank with filter floss, purigen and chemipure. Then to a small refugium before returning to the tank. This is my 3rd biocube I've set up the exact same way with amazing results. I've even gone to the extent of having my water tested by 2 different sources and we all come up with the same results. My only conclusion is the addition if this food. Whether I received a "contaminated batch" or not I will cease in using it from now on.

So sorry about your loss of fish. I wish we could pinpoint the cause. I have a thought that it may have been excess Nitrites. See below for my thought process.

You mentioned Purigen and Chemipure both being used. If I remember correctly, these are ion exchange resins from two manufacturers that each claim they remove Ammonia, Nitrite and Nitrate. I'm not criticizing the products but it may be worth noting that there have been complaints here on the forum in the past about these products causing problems. I personally used Purigen just recently. It was okay on the first pass but when I recharged and replaced it in the tank, something about my coral response told me to take it out. I believe something deleterious was being released into the water.

However unlikely, it is still possible that there was a reaction in the ion exchange resins upon introduction of the supplement. By description, the way an ion exchange resin works is that one ion takes the place of another ion on the resin surface. Something in the supplement could have traded places with ionic elements that had previously been removed from the water and held by the resin. If those ionic elements were kicked out to the water in significant quantities, Nitrites for example, fish could be killed as a result. Excess Nitrites can kill fish while coral remain unaffected.

If this indeed did happen, excess Nitrites would have been naturally processed by the tanks biofiltration so that Nitrites in the water could have already returned to acceptable levels by the time the water was tested.

I have had personal experience with promoting items for use in our tanks. I can vouch from personal experience that the people who develop and promote reef products are very interested in making their product better understood, of better quality and also making it right with us, the end users. I believe we would all appreciate and benefit if you were to talk to the distributor/manufacturer about your incident with this probiotic liquid coral food to see if the cause can be pinpointed.

Mahalo,
Mark