saltwater fish tanks

Question
QUESTION: there is a large saltwater fish tank at my work, lets say Ft width by
Ft. There were about 10 different fish inside. All of them died in one day...2
hours after the fish tank was cleaned. The fish tank cleaner guy said they died
due to poor feedings? that the fish food had been placed in the tank frozen..can
this happen?
the fish were fed approximately 1 sandwich baggy size of frozen fish food (containing shrimp, little silver fish, and assorted fish cubes. My assistants would defrost the food each morning as instructed and then feed the fish. The fish guy stated that the assistants were feeding the fish, frozen fish food and the fish were not eating it, so the food rotted in the tank... therefore killing the fish. Can this happen?


ANSWER: Hi Julia,
Was that 1 foot by 1 foot? If so thats an EXTREMELY small aquarium for ANY fish. In answer to your question, yes. If the fish eat frozen food it can kill them within minutes. If the fish aren't eating the food it sits in the aquarium and decomposes. It can cause an ammonia spike that will kill most of the fish available for aquariums. If they survive the ammonia spike, the next step is a nitrite spike, which is just as(if not more) lethal to your fish. This will also kill most of the aquariums inhabitants. It will usually take 2-3 days for this to happen and this cycle to start. How often was your aquarium cleaned and serviced? Was the water smelly, cloudy or murky? There are signs of this cycle happening in your aquarium. If there were no signs of clouding, murkiness or an odor, I would be more apt to believe that the fish recieved a different shock or instability in their environment. Toxins, drastic change in temperature or water quality. Without knowing the species of fish you kept, and water quality readings I cant be more specific or give you a definitive cause. But frozen foods can wreak havoc in an aquarium. Let me know if you have any more information or questions. I'll be glad to help.

---------- FOLLOW-UP ----------

QUESTION: im sorry for the typo. The fish tank is approximately 8ft by 4ft. Quite large. It gets serviced each week. No smell. There was an eel in the tank that passed days before the tank was serviced. There were orange looking nemo fish, blue thumb size fish, yellow looking angel fish? clown fish, angel fish, eel.

Answer
Julia,
In an environment that size I cant imagine the quantity of frozen food gathering needed to pollute the tank enough to kill its inhabitants. That leads me to believe that some other disturbance/shock to the environment took place. In a tank that size, being serviced every week, the food simply would not accumulate or reach a toxic level of ammonia or nitrite for quite some time. A simple matter of dilution. Too many gallons, too little food. I would look for other explanations. A cleaning agent used near by, contamination, heating being turned off, something sudden and drastic to impact the whole community in such a way. Look at the placement of the aquarium, have someone watch the next time it gets serviced. Simple mistakes, such as not turning on the power after servicing or cleaning a near by window with a spray, can have devastating effects on our aquatic pets. Did the service also provide the inhabitants? Or give advice as to when it could be repopulated? These answers will also be a key indicator as to your problem. If ammonia spike or contamination was the culprit, then it will have to cycle again, or be drained and cycled and could be 2-3 weeks before a population is reintroduced. If something else, then they will encourage repopulating quickly. Im sorry for the loss.