Lots of Dead Fish

MrSpecial

Reefing newb
I am having problems with most of my livestock dying in my saltwater aquarium. It is a 150 gallon FOWLR tank and has been running for about 5 or 6 months. We do not use a quarantine tank, and I do not believe we will be using one anytime soon :(. My 2 Tomato Clownfish and Longnose Hawkfish have been doing fine for about a month since we've added them. They do not express any odd behavior, whatsoever.

I have had the following 6 fish die, most after about 1-2 weeks of tank-life:
  • Raccoon Butterflyfish (after 1 week)
  • Longfin Bannerfish (1 week)
  • Sailfin Tang (1 week)
  • Sleeper Goby (4 weeks)
  • 2 Green Chromis (4 weeks)
  • Raccoon Butterflyfish (2 weeks)
They all seemed to feed well. Only on the day they died did I notice them either breathing very quickly and/or swimming on one side. I have checked the fish and I could not locate any other signs of disease (such as spots or unusual lines). The fish do not look like they are bullying each other; they usually kept to themselves (except for the 2 clownfish).

I have checked my water parameters; ammonia and nitrite readings show no traces of either, the pH level stays around 8.2-8.4, and the nitrate is at 20 mg/l. I realize that the less nitrate you have the better your tank is, but I also heard that 20 mg/l is not enough to kill most fish. I change 10% of the water every week, and I use saltwater that has been sitting for a day. The salinity is fine as well.

I am new to this hobby, but after a little research, the only possible solutions that make any sense to me are either increasing the tanks aeration, or lowering the salinity to get rid of any parasites. I would really appreciate insight anybody could give me.
 
Your nitrates are nowhere near what they would have to be to kill fish.

How do you acclimate your new fish? Do you just dump them in the tank, or do you drip acclimate them or float them?

Have you bought all the fish from the same store or did you get them from different places?

If you are not seeing any signs of disease, I doubt it's a parasite.

How many powerheads do you have? Do you have good water movement? Do you have a lid on your tank? Do you have a protein skimmer? Could you test for dissolved oxygen? You would have to order a test for that.

What and how often are you feeding?

How quickly after one another did you add the new fish?
 
We acclimate the fish by putting him in a bucket with the store's water in it. Then within the time span of around 30-40 minutes, I slowly add some of the water from my tank into the bucket. After 30-40 minutes, and there is the same amount of tank water as the store's was in the bucket, I add the fish to our tank.

All the fish have come from the same store.

We have 2 powerheads at the bottom of the tank, but don't seem to be moving the water too much. There is a tank lid and we do have a protein skimmer. I don't have a test kit for dissolved oxygen.

I am feeding the fish twice a day (1pm and 5pm) using pellets and frozen food.

We have been adding new fish to the tank about 2-3 weeks after the fish before it dies.
 
Okay. Move the powerheads to the top of the water so that they are breaking the surface. You NEED surface agitation. I would also add another two powerheads for a total of 4. Again, breaking the surface of the water so that the water is oxygenated. Remove the lid on the tank and replace it with eggcrate (you can find it in the lighting dept. at Home Depot or Lowes). Cut the eggcrate to fit the top of your tank. You need lots of surface agitation. I suspect that a lack of oxygen may be your problem. Also try getting a fish from a different store and see if that makes a difference.
 
That would be a big NO on the air stone.Airstones will only cause micro-bubbles and salt creep.

I have to agree with Biff and Reef on the power heads.

You might want to check for stray voltage too.Ive seen that kill fish but not be enough to tickle you when your working in the tank.
 
Ooooh good one Yote! I hadn't thought of that! Some of your equipment may be faulty and could be putting out a current in the tank. Sometimes it's not enough to outright kill them, but it can stress them enough that they eventually die. Check for that too.
 
Yeah Biff.
When he posted that they were fine,then all of a sudden were swimming on their sides and acting strange,I remembered seeing a tank with 2 jawfish do that at Bermuda.While checking the jawfish,we noticed that the light on the heater was flashing off and on,and when we checked it,there was a small crack in the glass which had let some water in.In short there was some low voltage current running through the tank,which killed both of the fish.
 
i think if you have more water movment the less ich you will get because the fish go near it and it and it gets all the fish off
 
I would recommend you lower the salinity and increase surface agitation at the same time. once you have treated with low salinity gradually increase it and keep the additional surface agitation going. add more pumps if needed. I suspect your difficulty is low oxygen or a parasite you cannot see, i.e. gill flukes, etc.
 
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