What killed my fish?

[perocchit]

I have a 25 gallon salt water tank and am new to this. I am hoping to get some insight.

We did a fishless cycle for a month, tested nitrate, nitrite, ammonia, phosphate, calcium, alkalinity and magnesium. Once all levels were good, we introduced two clown fish along with a few snaps and hermit crabs. A few weeks later we kept testing the water and added a ruby red dragonet, a sand sifting gobie, and an anemone over the course for 3 weeks with two corals that were installed about a week ago.

Everything was fine until today. I went to the store and got a 2nd ruby red, along with a couple hermit crabs and turbo snails. Water was tested 2 days ago for everything previously listed. I also got copepods a d zooplankton which got added today with the red dragonet, snails and hermit crabs.

I left today around 4:30, enjoyed looking at the fish one more time going out the door. I got back around 7:30 pm and it was crazy. The water was super cloudy, the dragonets were dead, the clownfish kept rushing up to the surface and eventually got lethargic and died. The sand Gobie jumped out of the tank and died on the floor and as I am rushing to mix more salt water for a water change, the anemone and corals are slowly dying. I tested everything mentioned above and everything is in normal range. What happened? I can’t figure it out. The closest thing I have found is the same symptoms as copper poisoning, but I only use RODI water and check the salinity every time I do a water change. I dunno if maybe too much zooplankton or copepods changed something? Any ideas?

 

[DCR]

Pretty sure it was a lack of oxygen, most likely due to a bacterial bloom that consumed the oxygen. Your clowns were rushing to the surface to get oxygen. I would suspect it came from the copepods or zooplankton you added. You added a bunch of bacteria food.

 

[Jekyl]

Few issues going on here. Firstly a 25g cannot house a mandarin, especially when the tank is brand new. They require pods to survive and generally want a 50g or so for even 1, and an established one at that.

Anemone are also in need of a mature system. Generally 6 months or more before attempting.

Do you practice any quarantine methods? All fish eating before? Any rapid breathing or damage to the fish?

Things in this hobby are best done slow and with a little research. It's hard to pinpoint cause of death after the fact. Could be illness, starvation, ammonia spike, aggression etc...

 

[perocchit]

Pretty sure it was a lack of oxygen, most likely due to a bacterial bloom that consumed the oxygen. Your clowns were rushing to the surface to get oxygen. I would suspect it came from the copepods or zooplankton you added. You added a bunch of bacteria food.

Well, I have been staying up all night to do water changes. Every couple hours changing a few gallons of water. Looks like the coral are fine, the anemone looked like it was struggling but is back to blooming since the water changes.

Are you saying adding too much copepods and zooplankton took too much of the oxygen from the water? Do I have to recycle the whole tank or just wait it out?

 

[DCR]

Yes, I think you probably added too much zooplankton which fed the bacteria and caused a population explosion. I don't know how much surface agitation/skimming you have, but in a small tank like that it is critical to maintaining high dissolved oxygen levels. You might want to keep some airstones and an air pump around in the event something like that happens again. The cloudiness of the water is indicative of a bacterial bloom. You don't need to cycle the tank again. Just let the bacterial bloom run its course. I would agree that you may need to slow down on the livestock you are adding to your tank, although I don't think that caused this wipe out.

 

[perocchit]

Few issues going on here. Firstly a 25g cannot house a mandarin, especially when the tank is brand new. They require pods to survive and generally want a 50g or so for even 1, and an established one at that.

Anemone are also in need of a mature system. Generally 6 months or more before attempting.

Do you practice any quarantine methods? All fish eating before? Any rapid breathing or damage to the fish?

Things in this hobby are best done slow and with a little research. It's hard to pinpoint cause of death after the fact. Could be illness, starvation, ammonia spike, aggression

Yes, I think you probably added too much zooplankton which fed the bacteria and caused a population explosion. I don't know how much surface agitation/skimming you have, but in a small tank like that it is critical to maintaining high dissolved oxygen levels. You might want to keep some airstones and an air pump around in the event something like that happens again. The cloudiness of the water is indicative of a bacterial bloom. You don't need to cycle the tank again. Just let the bacterial bloom run its course. I would agree that you may need to slow down on the livestock you are adding to your tank, although I don't think that caused this wipe out.

Thanks so much.

My wife and I have already talked about it, we are gonna wait a few weeks before adding any fish and just let the coral and the anemone do its thing. I will definitely look into air-stones or an air pump. This sounds right since I got a bottle of ‘concentrated’ zoo plankton. I added the bottle like I did with my copepods and when I saw how much actually was in there I used the fish net to scoop 80% of them out because it looked like a swarm.

I appreciate you responding to me. I am new to this, and what sounds like common knowledge to some we have never heard of. We are constantly finding out about things we didn’t know about. As of now, we probably are gonna wait a couple weeks than add a couple clown fish again and leave it at that for a while.

 

[DCR]

Be cautious adding anything to your tank as it can often have a negative impact. Always go slow with a smaller dose than recommended at first and observe. I would encourage you to be patient and let your tank mature naturally and not try to rush things with additives.

 

[perocchit]

Be cautious adding anything to your tank as it can often have a negative impact. Always go slow with a smaller dose than recommended at first and observe. I would encourage you to be patient and let your tank mature naturally and not try to rush things with additives.

Thanks again,

I just finished my last 2 gallon water change for the night. The corals and anemone are good, along with the hermit crabs and snails. Just the fish we lost tonight. I changed probably a total of 3 water changes, each about 3.5 gallons each just freaking out about not loosing the anemone and coral. We have added the water to the tank each 3.5 gallons we have taken away trying to bring oxygen and take away whatever else that may be harming it. 3 water changes, each one adding to the water and taking it out from the entire body of it, I guess mathematically we have changed 5.25 gallons of water (ish) considering we are adding the water to pre-existing water and then changing that 2 hours later.

Not looking to challenge math brainiacs or expert “none the better” aquarium owners, just trying to accurately list my actions for the next person who does the same thing. I was so upset when all these fish died, the dragonets were dancing together and the clown fish were were jumping in the wave maker and almost ‘surfing’ each wave. Definitely don’t want someone else to experience this.

Double check the bottle instructions and listen to this guy. Will try clown fish again in a couple weeks. We will see what we do after.