Fish dying...any help appreciated


New member
Hi there,

I'm afraid this may be long, but I want to give you all the info you need to help us out. We have been working hand in hand with someone at the store who we felt was very knowledgable, but now I'm beginning to worry and need of some fresh eyes and advice.

We have a 96 galloon tank which has been operating for 5 yrs (yes I know the tank isn't actually a newbie, but I'm a newbie to helping my boyfriend with it for the last several months and could use the help). Last summer we added 3 fish to the exisitng 4 which had been co-habitating nicely, and they (the original 4) proceeded to attack and destroy the one fish within an hour. Okay, bad call on the type of fish to buy, it happens. Then, within 3-4 days all of the other fish started dying until we are left with a lone electric blue damsel which lived by itself from August to December when we finally decided to give the tank another go. (We were quite distressed obviously, especially by the deaths of the original 4 fish who had lived happily for 2 years together).

Anyway, in late December we talked to the main fish guy at our local Big Al's about what had happened and we put in a little clown fish to see how things would go with him. He and the damsel did nicely for another 2. 5 weeks, so we decided to forge ahead. We purchased a Yellow Tang, and a little puffer. Aside from a major algae bloom, which we used Algone to treat, turned the lights off, and added a UV sterilizer, all seemed fine with the fish. Each week we added a couple of more fish (we only bought fish which had already been held at the store and survived nicely there for at least a week after arrival). We lost a Flame Angel several weeks ago, but it seemed to be an isolated incident. We waited 2.5 weeks before adding anything else to be sure that all was stable.

As of last Wednesday we had
- 1 Yellow Tang, 1 Copperbanded Butterfly, 1 puffer, 1 electic blue damsel, 3 domino damsels, 1 tiny clownfish, 5 green chromis (tiny ones), and a cleaner shrimp.

We are using an Eheim professional series pump, a protein skimmer (not sure of type or size, but it's pretty big), and a UV sterilizer that we added in January. We have 2 power heads circulating water (one is aimed at the surface to create a wave break). We have live rock (no coral),a nd a shallow sand bed.

Last Wednesday when we went to buy new substrate for the pump, our fish "pro" said we should not be using rock substrate as it's competing with the live rock, and performs the same function. He advised that we should be using these filtering pads (they came in a box, 2 white, one blue, and look similar to a scrubber pad for dishes (Iexcept the colour). I hope you can decipher the product I'm talking about. On this day we also purchased 5 green chromis and a cleaner shrimp.

On Thursday one chromis was dead. Friday another died. We felt this might be because they were so tiny and the domino damsels chased them around for hours and likely stressed them out. We changed the filter over from substrate to filtering pads as suggested (though I have to admit that part of me couldn't understand why we should be dumping all the substrate at once since we know there are good, necessary bacteria in there, but we followed his advice. So, that was Friday.

On Monday am we lost the Tang. Monday pm the Blue damsel. Wednesday am the puffer, Wednesday pm the Clown. This morning one of the domino damsels was dead. We called the store today but our "pro" wasn't there. Called another store and got told that we never should have changed the substrate and that's why all the fish are dying. My boyfriend just returned from the store now, and spoke to "our guy" who said there are differing opinions on the substrate vs. filter pads, but in his opinion for our set up his recommendations were the best.

Our water tests are
Ph 8.1 Nitrites 0.25 Ammonia 0 Nitrates 60 (a bit high, and we're using a NItrate sponge media bag in the filter as well as Algone) Salt is 1.023

We have been doing 10-15% water changes every other day since Friday when we lost the Chromis.

I should mention that the dying fish have no noticeable visual cues to any disease (no spots or anything) and they usually seem active and feeding well until about 24 hrs before they die when they become listless, and end up either "hanging at the top" or resting on the bottom. The tang and damsel did become slightly paler than normal before they died, but none of the other fish have exhibited this symptom. if you can. My better half is ready to close the tank if the rest of the fish die (which I can't blame him) but I'd really like to try to stop the cycle of death if possible. Also, opinions of the filtering media debate would be welcome as if this is the cause of the problem we'd like some ammunition to go back into the stire with since we did it on their advice.

Thanks in advance,


Life and Reef Saver
Where are the filter pads going? Are you using an undergravel filter? The removal of the old substrate, which sound like crushed coral, probably released 5 years worth of "crap" that was built up in it.

Your nitrates aren't bad for a fish only aquarium. The use of product like Algone and Nitrate sponges shouldn't be necessary if regular water changes are done, the tank isn't overstock, and over feeding is being practiced. They are a waste of money, IMO, and causing the death of all the algea in the tank at once can cause shifts in pH and oxygen levels due to the rapid decay of algae.

I am a bit confused about how your set-up is arranged so if you can post photos, it would be very helpful.


New member
the first lot of fish that died, it seems was a teritory battle that pretty muched killed all the fish n stressted them to death.

Just From my understanding, it seems to me you have increased your bio loads substantily in a short space of time, while removing your live substrate, whioch probably had loads of benifical bactiria in it.

it could just be this simple, your first chromis died and put an increase of amonia in the tank, with your already heavy bio load this, meant your filtration wasnt coping with the amonia in the tank and it posioned all your fish, i say this because you have Nitrite which in it self is posion for fish, and if you have some of that, then you had amonia before.

How big is your tank? that many fish only 2 power heads?

oh 96 gallons? what is your turn over i mean 2 power heads in a 96 gallon?


New member
Were all the fish found and promplty removed after death?

I assume when you are talking about changing substrates your really talking about the filter media, right?

It sounds like the first set of fish may have died either from stress (I can't believe you actually added a damsel to an otherwise peaceful, mature tank!), or from increasing the bio-load too quickly, or possibly from a disease/parasite introduced with the new fish..

All the recent additions most likely died of ammonia poisoning, as the increase in bio-load was rapid, and combined with the changing of the filter media.

The first thing I would say to do different is to not make so many rapid changes. When changing out the filter media, it should have been done in stages of 1/2 to 1/3 at a time, with a couple of weeks in between. New fish should not have been added during this time. When adding new fish, it is best to add one or two at a time, not 5 or 6, again, with a couple of weeks in between.

Your fish "pro" was right about the media in the filter, but he was way wrong in not telling you to do it in stages, and for selling you new fish at the same time he advised you to do this.

The bio-filter in a tank is a very delicate balance between the waste being produced and the bacteria that consume that waste. There are not just extra bacteria sitting aroung waiting for more waste. If they are not needed (not enoughh waste to feed them) they die off. Increase the waste, and the bacteria need time to multiply in reponse. Remove a huge colony of bacteria (like in your filter media) and the remaining bacteria need time to adjust just to the load that's always been in the tank, nevermind the new additions.

Also, you really should quarantine all new additions for at least 4 weeks before you add them to your tank, or you risk them carrying a disease that wipes out your entire tank.


Premium Member
Changing the substrate can cause issues, but usually doesn't, IME. I've done it twice. What was the old substrate, and what is the new?

About the filter pads, what brand, etc, are they, and did you take out anything other than substrate?

I agree that that's a fast schedule for adding fish, and they're not particularly compatible. I suspect that the problem is a fish disease or aggression, or both. I agree that a quarantine tank and a slower schedule for adding fish would likely help a lot. In the mean time, I don't know much that you can do except wait to see how the tank settles.

If you could list all the filtration equipment and any more water parameters, we might be able to comment more. How much live rock is there? What kind of powerheads do you have? Two might not be enough for that large a tank. What other circulation is in place?


New member
bertoni, are you talking about an actual substrate (like a sand bed in the bottom of the tank), 'cause I got the impression she was talking about some type of filter media, like ceramic rings or something, in the canister that she replaced with the sponges.

Sounds like flow is provided by the 2 powerheads plus the canister filter and a skimmer. Seems like plenty for FOWLR, no?


Premium Member
Hmm, I was talking about a substrate, but you're right, she might be talking about a filter. I'm confused.

Well, it's a 96g tank, and live rock doesn't necessarily work all that well without filtration, so without knowing what the powerheads are, I am hesitant to say that the circulation is okay.


New member
Thanks for your ideas so far.

Just a bit of clarification. The two power heads which are placed right in the tank to help with circulation & making waves, are in addition to the Maxi Jet 900 on the protein skimmer, and the Eheim pro pump aet/dry filter.

ALso to clarify the original problem last summer. We didn't just add a damsel. We had 4 stable fish for 2 yrs. A spanish hogfish, Niger trigger, picasso trigger and Yellow tang. We added 3 fish, 2 blue damsels and one fish whose name I forget offhand, but it had a large plume off the top and bottom of it. The 4 main fish attacking it was obviously a terriorial issue. We know that. Why all the fish died immediately after eating the poor thing until it died, I don't know except that we figured the fish that they ate was sick, and they then became sick. THe only one who survived was one of the blue damsels.

Also we know that we shoud only add 1-2 fish at a time generally, but the chromis were literally babies, and all together, were smaller than one large fish. At least we were told it would be okay becausxe they were so small.

It is not he sand that we changed (didn't touch that) It is the filter media inside the filter we're talking about. We also know that NORMALLY you never change all the filter material at once (which is why I had a sick feeling when we were doing it) Reverend Mayanrd (I'm noticing your tag line....I never should have just gone ahead with this I guess). But we did ask twice, and confirm to change it all at once. I'm thinking now, if he wanted us to change to the filter pads, we should have at changed one tray to a pad, at a time. Isn't hindsight wonderful?

Does this help clarify things?



New member
Sorry missed the live rock question....there was at least 30-35 pounds originally (we forget how much, it was bought 5 yrs ago) and we added another 13 pds on Wednesday as well...sorry forgot about the addition of the live rock as another change.


New member
Oh yes, one more thing, we are removing dead fish immediately. The only one that didn't get removed immediately was one of the chromis was literally so small that we couldn't find it when it died. Even searching for it we couldn't find it anywhere. When it's clear a fish is going to die, do they ever recover or should we just remove it when it's gotten to the point that it's obviously a goner so that we don't have to look for it later, and risk not finding it at all?


New member
Yes, I think it does. Except...

What brand/model are the powerheads?

You still have some living fish?

Maybe you could post a pic so we can guesstimate how much rock you have? If it's really that little, it sounds like too little for adequate filtration in that size tank, especially if you want to keep 10+ fish.

This live rock you added, was it fully cured?


New member
THe powerheads are Maxi Jets. There is a 900 on the protein skimmer. A 400 is pointed horizontallf from the back of the tank on the opposite side of the protein skimmer and intake/outtakes for the filter. There is a 600 pointing towards the surface. The filter is an Eheim Professional 2227. According to the specs on the Eheim site this filter falls into the category for tanks over 200 gallons. So it should be more than powerful enough. The protein skimmer is a Berlin, and says it's suitable for up to 250 gallons.

Yes there are still living fish, a Copperhanded butterfly, a diana wrasse (that I missed in my first listing), 2 Domino damsels, and 3 very small green chromis, plus the cleaner shrimp. We've lost 7 of the 15 living guys so far in one week.

The live rock was in the aquariums at the fish store, and was taken from their active tanks that had fish in them.

I will try and get a pic but the living rock extends approx 40 - 50% the height of the tank and 70- 80% of the width (of course there are lots of swim throughs and places to hide....but just to try and give you more of a visual.

Also temp is 84 F.

How could it be ammonia poisoning if the ammonia has never been more than 0 and to clarify Josh, the Nitrite is .25 it was the nitrates that have been higher than they should be.

I'm hearing all of the good suggestions about how to prevent this in the future, but any suggestions on anything more we can do now, except wait and see?

Thanks to you all,


Premium Member
The powerhead on the protein skimmer is pumping mostly air, so it doesn't add much circulation. The 400 and 600 are pretty weak. I don't know how much water that filter moves. I'd aim for a total of at least 1000 gph or so for the tank. That might help the live rock function better.

I'm not convinced it was ammonia poisoning. The tank might have had a transient spike in ammonia, I suppose, but I would guess that the problem lies elsewhere.


New member
That temp seems a bit high. There have been polls recently, and the majority of reefers seem to keep their tanks between 78-80f.

That sounds like adequate live rock, but the flow does seem pretty low. You could step up the in-tank powerheads to 1200s (much cheaper on line, around $20 each). They are the same size, they just pump more water. One at each back corner, pointed toward the middle of the front glass, on a slightly upward trajectory (for surface agitation) works pretty well. Or, if your real ambitious, you could add a closed loop to the system and get rid of the powerheads all together.

I say ammonia poisoning because of the disruption to the filter media and the addition of a large number of new fish. Test kits are not always accurate, nor necessarily performed at the right time. The results you posted that showed positive for nitrites could have been taken after the ammonia was processed out by the resurgent bacteria. Obviously, I'm guessing, but your symptoms do match the profile. Low O2 could also cause these symptoms, which, with your relatively low flow and high temp, could be the problem. In fact, after typing that, it seems like an even better candidate.

Is there any accumulation of scum on the water's surface? This is a common problem on tanks that don't use overflows, and could disrupt gas exchange.

Any further deaths? All the fish are eating?


New member
I think you should lower the temp to 79 vicinity. Also, it seems like you like more aggressive fish, and that's ok, but expect them to battle, especially damsels. You can start out with 10 chromis in a tank and in a few months you'll have two. They fight a lot, chase a lot, and generally just harass everyone.
I don't recommend having any damsels or chromis because of this. And, they're a pain in the A** to catch if you want to get rid of them.
Good luck :)


New member
Thanks for the continued advice in trying to decipher the root of the problem. Yes, 2 more fish have died unfortunately. The butterfly and the wrasse. It seems inevitable that they'll all die at this right which is just so discouraging.

In retrospect, I wish we had done more research initially, and not blindly trusted the guy at the fish store. I guess we thought a marine biologist should know what he's talking about. He was familiar with our entire set up and knew each fish we had and we only bought new fish after consulting him. As I said, it's just so discouraging.

I've lowered the thermostat (we raised the temp on the fish guy's advice of was 79-80 until the flame angel died in what seemed to be that isolated event (at the time) 3-4 weeks ago. He tried to blame the temp, and suggested we raise the tank temp slowly.

I'll change the power heads for more powerful ones, lowered the temp, but is there anything else I can do? Is continuing to do 10% water changes worth the effort at this point?

Also, RL, thanks for the insight on the fish. Of course we were never warned about the aggressiveness of the damsels, and we only noticed their behaviour when something significantly smaller was introduced. However thinking back the blue damsel did try to "take on" the Tang (a large one) when it was first introduced. It looked like a grade one kid taking on an 8th grader, lol! Of course we just figured it was normal given that the damsel had lived on his own for many months. Anyway, we'll have to give more thought to that if they survive.

Down to all the $10 dollar fish now. 2 domino damsels, 3 chromis and the cleaner shrimp (well....he wasn't $10, but you get my frustration).



New member
<a href=showthread.php?s=&postid=6925803#post6925803 target=_blank>Originally posted</a> by reverendmaynard
Why would a marine biologist be working at a lfs?
Excellent question! Yeah, why is that?

Anyway, I wouldn't add anything else for a while. Wait and see if what you have in there dies. If you go 3 or 4 weeks and everything is still alive, test your water again. Make sure everything is stable. Get the damsels out of there (bring them back to the expert at the LFS and educate him about their aggressiveness ;) )
Then maybe try a normal fish :) that gets along with others.


Premium Member
Personally, I keep my tanks at 82, and think that's a fine temperature. Both the chemistry forum and have articles on this issue, if anyone wants to do some reading. 84 is on the higher end, but not too bad, IMO.