Dead Fish - Why?

[Ron99]

Well, it was an unhappy morning for me. I have a 10 gallon I set up around Christmas. It had only live rock, soft corals and the CUC until the weekend. Went and picked up an orange spot shrimp goby, a royal gramma and a clown goby on Friday night. All were acclimated properly and seemed to be doing well for 2 days. They were moving around the tank and even eating a bit. Then woke up yesterday morning to find them all dead.

I am hoping for some insight into what might have killed them all. They didn't have any spots that looked like ick or velvet etc. All the corals and inverts look fine. Just the fish are dead.

My only idea is that maybe the oxygen levels dropped too much at night when all the photosynthesis stopped and everything in the tank was using oxygen up. I have good water circulation with a koralia nano and a HOB aquaclear filter splashing water back in which I assumed would be enough water movement to keep the water oxygenated. Salinity was 1.026 and ammonia, nitrate and nitrites were all 0. pH is about 8.2.

I don't want to get any fish again until I have some idea what might have done this. Is there any possible contamination in the tank that would specifically kill the fish and leave the inverts unaffected?

Thanks in advance for any insights,

Ron

[Flash]

i would have let your tank cycle a little longer before adding fish just to be safe.... could have been bad water? temp??

[Snaz]

I suspect it was too many fish to soon. A new 10 gallon tank just does not have enough capability to handle three fish all at once.

Next time add the fish one at a time, leaving at least 3 weeks between purchase of each fish.

[pinhead]

I'd say it is a circulation problem rather than some contaminant or adding fish too quickly. If your corals were not affected and the fish were fine during the day it has to be the difference between the daytime conditions and night time.

During the day, the photosynthetic corals and macroalgae are undergoing photosynthesis where:

carbon dioxide + water ---> glucose + oxygen

So during the day oxygen levels are high and the fish are happy.

At night, the reverse is true and the photosynthetic organisms are undergoing aerobic respiration using up the sugar they produced during photsynthesis:

glucose + oxygen --> carbon dioxide + water

So your corals and macroalgae are now competing with your fish for oxygen. As well, the carbon dioxide is converted into Carbonic acid and the pH drops.


So your fish become stressed and may even suffocate and die.

I would imagine your flow at night is not agitating the surface water and getting oxygen to the bottom of the tank where the gobies live. I don't think I've seen gobies go to the surface to try to gulp down air and even if they did, they would sink back to the bottom.

Re-aim your powerhead placing near the surface to force water down to the bottom or at the bottom to move water to the surface. I bet it is just flowing linearly parallel to the surface.

Or add more flow with more powerheads.

[naesco]

Well, it was an unhappy morning for me. I have a 10 gallon I set up around Christmas. It had only live rock, soft corals and the CUC until the weekend. Went and picked up an orange spot shrimp goby, a royal gramma and a clown goby on Friday night. All were acclimated properly and seemed to be doing well for 2 days. They were moving around the tank and even eating a bit. Then woke up yesterday morning to find them all dead.

I am hoping for some insight into what might have killed them all. They didn't have any spots that looked like ick or velvet etc. All the corals and inverts look fine. Just the fish are dead.

My only idea is that maybe the oxygen levels dropped too much at night when all the photosynthesis stopped and everything in the tank was using oxygen up. I have good water circulation with a koralia nano and a HOB aquaclear filter splashing water back in which I assumed would be enough water movement to keep the water oxygenated. Salinity was 1.026 and ammonia, nitrate and nitrites were all 0. pH is about 8.2.

I don't want to get any fish again until I have some idea what might have done this. Is there any possible contamination in the tank that would specifically kill the fish and leave the inverts unaffected?

Thanks in advance for any insights,

Ron

The answer is very simple. You put too many fish in your tank at the same time and put the bioload out of order. At the very minimum in a tank your size I would only put one fish every two months.
BTW I would also not get a gramma as they are too aggressive in a small tank. I would put the orange last like 6 months from now to give your sandbed a chance to grow lots of critter.
Successful hobbyist go very sllllllllooooooooooow.

[Black Phantom]

I'm with Snaz. Small tank not yet established plus 3 new fish = lots o poop = ammonia. Go slow.

[dsaundry]

Agree...Too many too fast in a small tank like that..It is most likely still cycling a bit as well still..small tanks have to have livestock added slowly.

[Ron99]

I would tend to go with the circulation/oxygen theory for a couple of reasons:

1. The rock and sand came from an established tank and was transported wet. There was an almost undetectable spike in the first week and since then all levels of ammonia, nitrate, nitrite, phosphate have been zero when i've tested the water. So no cycle to speak of.

2. The increased bioload did not seem to have any effect as I tested the water right after the fish died and all readings were still zero. Even if the fish were pooping up a storm they probably wouldn't die so quickly and suddenly as they did from increased waste in the water.

3. All the inverts and corals are doing fine. Good polyp extension on the leathers and the zoas are all open. Increased waste should have affected them as well.

So I think what I need to do is get my refugium going (have just been waiting for my led light to show up) and grow cheato in it with either a reverse day/night cycle or just light it 24/7. That will provide a constant source of oxygen to the tank. I will also try to rearrange the powerhead to get more surface agitation and exchange from top to bottom.

[Flash]

i have a 10gl nano.. i have lots of corals, two clowns and a cleaner shrimp

I am running a korila1 and a aquaclear 20 filter... my tank is just fine... more then enough water movement and oxygen!