Fish dying?

c.dickens9

Community Member
View Badges
Joined
Aug 4, 2025
Messages
61
Reaction score
19
Location
Raleigh nc
Rating - 0%
0   0   0
For the last week I’ve been dealing with my fish in my display tank just becoming extremely lethargic not eating and then laying on the ground. It’s a relatively new tank moved them from a 33 to a 60 about a month ago and they randomly are dropping like flies. Then when I move them into my 15 gallon cube that’s been running for a few months they fully recover and are fine but if I put them back in main tank they become lethargic don’t eat and are on the ground again. Also noticed my clown’s top fin is becoming translucent. Haven’t had any parameter swings and even changed my water a few days ago which throws me for a loop even more. I just run a HOB with media and activated carbon but any advice helps all my inverts and coral seem completely unaffected by whatever is happening.
20260131_185236_0EB4F6D1-6802-432F-9293-B270EEAB578A.png
 

Mr. Mojo Rising

10K Club member
View Badges
Joined
Feb 14, 2021
Messages
13,336
Reaction score
15,812
Location
Toronto
Rating - 0%
0   0   0
Just a hob in a 60 gallon, nothing else? Do you have powerheads for surface agitation, how is the water oxygenated? Inverts need less oxygen than fish.
 

W31Olds

Valuable Member
View Badges
Joined
Dec 13, 2024
Messages
1,784
Reaction score
1,529
Location
Timonium
Rating - 0%
0   0   0
How is respiration rate? I would check your Ammonia levels an add an Airstone. I agree, a HOB filter may not be sufficient.
 

vetteguy53081

Well known Member and monster tank lover
View Badges
Joined
Aug 11, 2013
Messages
108,086
Reaction score
242,646
Location
Wisconsin -
Rating - 100%
17   0   0
For the last week I’ve been dealing with my fish in my display tank just becoming extremely lethargic not eating and then laying on the ground. It’s a relatively new tank moved them from a 33 to a 60 about a month ago and they randomly are dropping like flies. Then when I move them into my 15 gallon cube that’s been running for a few months they fully recover and are fine but if I put them back in main tank they become lethargic don’t eat and are on the ground again. Also noticed my clown’s top fin is becoming translucent. Haven’t had any parameter swings and even changed my water a few days ago which throws me for a loop even more. I just run a HOB with media and activated carbon but any advice helps all my inverts and coral seem completely unaffected by whatever is happening.
20260131_185236_0EB4F6D1-6802-432F-9293-B270EEAB578A.png
I dont believe this is a water quality issue, but possibly something in new tank possibly decay from a lost fish, or false test readings but if this were the case, you would see labored breathing, gasping at surface and fish hiding.
Are there any inverts and coral in the new tank and how are they looking ?
 
OP
OP
C

c.dickens9

Community Member
View Badges
Joined
Aug 4, 2025
Messages
61
Reaction score
19
Location
Raleigh nc
Rating - 0%
0   0   0
For the last week I’ve been dealing with my fish in my display tank just becoming extremely lethargic not eating and then laying on the ground. It’s a relatively new tank moved them from a 33 to a 60 about a month ago and they randomly are dropping like flies. Then when I move them into my 15 gallon cube that’s been running for a few months they fully recover and are fine but if I put them back in main tank they become lethargic don’t eat and are on the ground again. Also noticed my clown’s top fin is becoming translucent. Haven’t had any parameter swings and even changed my water a few days ago which throws me for a loop even more. I just run a HOB with media and activated carbon but any advice helps all my inverts and coral seem completely unaffected by whatever is happening.
20260131_185236_0EB4F6D1-6802-432F-9293-B270EEAB578A.png
I dont believe this is a water quality issue, but possibly something in new tank possibly decay from a lost fish, or false test readings but if this were the case, you would see labored breathing, gasping at surface and fish hiding.
Are there any inverts and coral in the new tank and how are they looking ?
I did see labored breathing and assumed it was a lack of oxygen issue so I got a new large air stone and pointed both powerheads at surface to no change in results.
 
OP
OP
C

c.dickens9

Community Member
View Badges
Joined
Aug 4, 2025
Messages
61
Reaction score
19
Location
Raleigh nc
Rating - 0%
0   0   0
Just a hob in a 60 gallon, nothing else? Do you have powerheads for surface agitation, how is the water oxygenated? Inverts need less oxygen than fish.
Sorry I have two power heads and large air stone as well just meant hob as my filtration not a sump or canister
 

Jay Hemdal

10K Club member
View Badges
Joined
Jul 31, 2020
Messages
37,573
Reaction score
37,369
Location
Dundee, MI
Rating - 0%
0   0   0
I did see labored breathing and assumed it was a lack of oxygen issue so I got a new large air stone and pointed both powerheads at surface to no change in results.

It did sound like a low oxygen issue to me. If the air stone didn’t change things, the next question in would have is how are the non-fish, invertebrates doing in the affected tank? If they are thriving, that does push things towards a disease issue, but that doesn’t align with moving the fish and seeing improvement (as they would have moved the disease with them).
 
OP
OP
C

c.dickens9

Community Member
View Badges
Joined
Aug 4, 2025
Messages
61
Reaction score
19
Location
Raleigh nc
Rating - 0%
0   0   0
I did see labored breathing and assumed it was a lack of oxygen issue so I got a new large air stone and pointed both powerheads at surface to no change in results.

It did sound like a low oxygen issue to me. If the air stone didn’t change things, the next question in would have is how are the non-fish, invertebrates doing in the affected tank? If they are thriving, that does push things towards a disease issue, but that doesn’t align with moving the fish and seeing improvement (as they would have moved the disease with them).
Yeah right big puzzle 😭 the inverts (cleaner shrimp, blood red shrimp, emerald crabs hermit crabs snails) and corals are all fine but the fish are definitely not, lost my coral beauty overnight think I just moved him too late to the cube but yeah it’s really throwing me for a loop😭 everything I moved out early enough fully recovers
 

MnFish1

10K Club member
View Badges
Joined
Dec 28, 2016
Messages
26,916
Reaction score
24,616
Location
Midwest
Rating - 100%
2   0   0
Yeah right big puzzle 😭 the inverts (cleaner shrimp, blood red shrimp, emerald crabs hermit crabs snails) and corals are all fine but the fish are definitely not, lost my coral beauty overnight think I just moved him too late to the cube but yeah it’s really throwing me for a loop😭 everything I moved out early enough fully recovers
How many fish total are in the tank - and were in the tank at the start. Maybe I missed it - did you check parameters? Not all parameters that affect fish will affect invertebrates. However the fact that the invertebrates are ok make a parameter issue less likely. Are you running carbon in your new tank? (activated carbon)? - Additionally, which corals do you have - soft corals will be much more tolerant of issues than others
 
OP
OP
C

c.dickens9

Community Member
View Badges
Joined
Aug 4, 2025
Messages
61
Reaction score
19
Location
Raleigh nc
Rating - 0%
0   0   0
Yeah right big puzzle 😭 the inverts (cleaner shrimp, blood red shrimp, emerald crabs hermit crabs snails) and corals are all fine but the fish are definitely not, lost my coral beauty overnight think I just moved him too late to the cube but yeah it’s really throwing me for a loop😭 everything I moved out early enough fully recovers
How many fish total are in the tank - and were in the tank at the start. Maybe I missed it - did you check parameters? Not all parameters that affect fish will affect invertebrates. However the fact that the invertebrates are ok make a parameter issue less likely. Are you running carbon in your new tank? (activated carbon)? - Additionally, which corals do you have - soft corals will be much more tolerant of issues than others
I have some torches a trachy some hammers and a few mushrooms but not too much soft coral. The 60 gallon tank initially had two juvenile clownfish a bristletooth tang and a coral beauty. My parameters should be fine they only would’ve swung if any when I changed my water last week. First ones started acting strange were the tang and coral beauty, being lethargic, swimming strange, not eating and breathing heavily. Off of that I assumed it was an oxygen issue and added a bigger airstone and have two powerheads pointed at surface. Didn’t get better and started going into the sand so I moved both of them to a 15 gallon cube (clownfish unaffected at this point so left them in 60) both recovered over night so I put them back in the 60 and they went downhill after a day of being alright again. Was able to move the tang into the 15 again and he fully recovered and has been in it since. Couldn’t catch the coral beauty before he died so he died last night and by last night one of the clownfish looked horrible (ie: initial picture) so I moved him into the cube and now the spot where it looked like his fins were becoming transparent has gone back to normal and he’s now pretty much recovered by this morning in the cube.
 
OP
OP
C

c.dickens9

Community Member
View Badges
Joined
Aug 4, 2025
Messages
61
Reaction score
19
Location
Raleigh nc
Rating - 0%
0   0   0
Yeah right big puzzle 😭 the inverts (cleaner shrimp, blood red shrimp, emerald crabs hermit crabs snails) and corals are all fine but the fish are definitely not, lost my coral beauty overnight think I just moved him too late to the cube but yeah it’s really throwing me for a loop😭 everything I moved out early enough fully recovers
How many fish total are in the tank - and were in the tank at the start. Maybe I missed it - did you check parameters? Not all parameters that affect fish will affect invertebrates. However the fact that the invertebrates are ok make a parameter issue less likely. Are you running carbon in your new tank? (activated carbon)? - Additionally, which corals do you have - soft corals will be much more tolerant of issues than others
I have some torches a trachy some hammers and a few mushrooms but not too much soft coral. The 60 gallon tank initially had two juvenile clownfish a bristletooth tang and a coral beauty. My parameters should be fine they only would’ve swung if any when I changed my water last week. First ones started acting strange were the tang and coral beauty, being lethargic, swimming strange, not eating and breathing heavily. Off of that I assumed it was an oxygen issue and added a bigger airstone and have two powerheads pointed at surface. Didn’t get better and started going into the sand so I moved both of them to a 15 gallon cube (clownfish unaffected at this point so left them in 60) both recovered over night so I put them back in the 60 and they went downhill after a day of being alright again. Was able to move the tang into the 15 again and he fully recovered and has been in it since. Couldn’t catch the coral beauty before he died so he died last night and by last night one of the clownfish looked horrible (ie: initial picture) so I moved him into the cube and now the spot where it looked like his fins were becoming transparent has gone back to normal and he’s now pretty much recovered by this morning in the cube.
Also sorry yes I’m running active carbon as well
 

BubbleAlgaeFarmer

Active Member
View Badges
Joined
Jul 4, 2024
Messages
285
Reaction score
161
Location
Massachusetts
Rating - 0%
0   0   0
Interested to see what happens here. Only been at this for almost two years, so i’m still a noob. One thing that came to mind is perhaps getting an ICP test.
 

Puggz

Active Member
View Badges
Joined
Jan 16, 2026
Messages
165
Reaction score
113
Location
Ontario
Rating - 0%
0   0   0
Sounds like ammonia to me. Years ago I killed a subadult Passer Angle. Cleaned a bunch of fuzzy algae off my rocks and glass and let the canister filter clean it up. Forgot to clean the canister filter and it turned into an ammonia factory. Even after a big water change the ammonia would jump right up again. Learned a valuable lesson and lost a beautiful fish in the process.

Does the HOB perform all your filtration (Mechanical, Chemical,Biological)? Maybe its just not up to the task - I would think its not enough for a 60 mixed. Have you cleaned the filter media lately? Maybe some or all of the bacteria were removed and your tank is going through a mini cycle. I believe its always best to have 2 or 3 types of biological filtration. Live rock, media, and even a prefilter (sponge, floss) will work part time.
 
Last edited:
OP
OP
C

c.dickens9

Community Member
View Badges
Joined
Aug 4, 2025
Messages
61
Reaction score
19
Location
Raleigh nc
Rating - 0%
0   0   0
Sounds like ammonia to me. Years ago I killed a subadult Passer Angle. Cleaned a bunch of fuzzy algae off my rocks and glass and let the canister filter clean it up. Forgot to clean the canister filter and it turned into an ammonia factory. Even after a big water change the ammonia would jump right up again. Learned a valuable lesson and lost a beautiful fish in the process.

Does the HOB perform all your filtration (Mechanical, Chemical,Biological)? Maybe its just not up to the task - I would think its not enough for a 60 mixed. Have you cleaned the filter media lately? Maybe some or all of the bacteria were removed and your tank is going through a mini cycle. I believe its always best to have 2 or 3 types of biological filtration. Live rock, media, and even a prefilter (sponge, floss) will work part time.
Currently have bio balls, sponge and activated carbon in the HOB, started the tank with Liverock so that’s all the rock work. I tested 0 for ammonia the entire ordeal so if that’s what it is then not sure why it’s testing 0
 
OP
OP
C

c.dickens9

Community Member
View Badges
Joined
Aug 4, 2025
Messages
61
Reaction score
19
Location
Raleigh nc
Rating - 0%
0   0   0
Sounds like ammonia to me. Years ago I killed a subadult Passer Angle. Cleaned a bunch of fuzzy algae off my rocks and glass and let the canister filter clean it up. Forgot to clean the canister filter and it turned into an ammonia factory. Even after a big water change the ammonia would jump right up again. Learned a valuable lesson and lost a beautiful fish in the process.

Does the HOB perform all your filtration (Mechanical, Chemical,Biological)? Maybe its just not up to the task - I would think its not enough for a 60 mixed. Have you cleaned the filter media lately? Maybe some or all of the bacteria were removed and your tank is going through a mini cycle. I believe its always best to have 2 or 3 types of biological filtration. Live rock, media, and even a prefilter (sponge, floss) will work part time.
Currently have bio balls, sponge and activated carbon in the HOB, started the tank with Liverock so that’s all the rock work. I tested 0 for ammonia the entire ordeal so if that’s what it is then not sure why it’s testing 0
How did you end up fixing that?
 

MnFish1

10K Club member
View Badges
Joined
Dec 28, 2016
Messages
26,916
Reaction score
24,616
Location
Midwest
Rating - 100%
2   0   0
The one thing is that Coral is less sensitive to ammonia than fish - It would be really great if you could check a full set of parameters. Additionally - curious do the fish gulp air at the surface (more than likely an Oxygen problem) or are just breathing fast. Did you QT your fish - and have you added anything new when you upgraded your tank that might have brought a disease in, Again - disease shouldn't resolve - as @Jay Hemdal said - with changing tanks. It sounds like some kind of 'toxic issue' that coral is less susceptible to.
 

MnFish1

10K Club member
View Badges
Joined
Dec 28, 2016
Messages
26,916
Reaction score
24,616
Location
Midwest
Rating - 100%
2   0   0
Currently have bio balls, sponge and activated carbon in the HOB, started the tank with Liverock so that’s all the rock work. I tested 0 for ammonia the entire ordeal so if that’s what it is then not sure why it’s testing 0
This is interesting - and important to point out - many tanks can run just on flow and no filtration except live rock in the tank. The HOB is handy for putting in carbon, etc. I wanted to ask - when you move the fish from tank 1 to tank 2, how long does it take to improve (you kind of implied it was instant or near instant) - additionally if you put the fish back from tank 2 to tank 1 how long does it take to get worse (the fish)
 

Puggz

Active Member
View Badges
Joined
Jan 16, 2026
Messages
165
Reaction score
113
Location
Ontario
Rating - 0%
0   0   0
How did you end up fixing that?
Cleaned the filter canister, just the prefilter that had all the decaying algae in it. I had an undergravel system that took care of the biological load. It recovered really quickly
 
OP
OP
C

c.dickens9

Community Member
View Badges
Joined
Aug 4, 2025
Messages
61
Reaction score
19
Location
Raleigh nc
Rating - 0%
0   0   0
Currently have bio balls, sponge and activated carbon in the HOB, started the tank with Liverock so that’s all the rock work. I tested 0 for ammonia the entire ordeal so if that’s what it is then not sure why it’s testing 0
This is interesting - and important to point out - many tanks can run just on flow and no filtration except live rock in the tank. The HOB is handy for putting in carbon, etc. I wanted to ask - when you move the fish from tank 1 to tank 2, how long does it take to improve (you kind of implied it was instant or near instant) - additionally if you put the fish back from tank 2 to tank 1 how long does it take to get worse (the fish)
Everytime I’ve moved a fish it’s been right before I turn the lights out and they’ve completely recovered and are eating by the morning
 

TOP 10 Trending Threads

WHAT AMOUNT OF LIVE ROCK AND SAND SHOULD BE PRIORITIZED FOR OPTIMAL BIODIVERSITY/FILTRATION?

  • 100% live rock + bagged sand

    Votes: 34 27.9%
  • 100% dry rock + 100% live sand

    Votes: 42 34.4%
  • 50/50 live/dry rock, 50/50 live/bagged sand

    Votes: 27 22.1%
  • 75% live rock, 25% live sand

    Votes: 11 9.0%
  • 25% live rock, 75% live sand

    Votes: 8 6.6%
Back
Top