40 gallon - Why Are My Fish Dying?

Julie Rogers

I have a 40 gallon and a 20 gallon tank. In my larger one I used to have tiger barbs, Bettas, neon tetras, and other fish. All of the tiger barbs and bettas have since died, and one of the tetras. I don’t know why all the fish in there are dying. The barbs would stop swimming a lot before they died, often hiding in the hornwort or by a log I have. The bettas would be fine one minute and the next be dead. I constantly check my water parameters to make sure they’re normal. They are besides the phosphates being somewhat high, although I’ve been working to get them down. In the 20 gallon I had a couple of green barbs, dwarf gourmis and an Oscar. One of the barbs, both the gourmis, and the Oscar have died. The gourmis were the same as the bettas... fine, then dead. And the Oscar took 5 days to die. He’d lay on the bottom of the tank and move every once in a while but stopped eating. Again, the water levels are okay. Does anyone know what might be going on?
 

Zigi Zig

Hello
We need to know more about your tank not just (my water is ok) what is your ammonia level,PH, Temp, when was the last time you change water, what kind of filtration do you use
 

!poogs!

Hello
We need to know more about your tank not just (my water is ok) what is your ammonia level,PH, Temp, when was the last time you change water, what kind of filtration do you use

And,

Are they both new set ups?

Did you add the fish all at the same time, or around the same time?

FYI, the fish in your 20 gallon tank are not compatible.
 

Julie Rogers

Hello
We need to know more about your tank not just (my water is ok) what is your ammonia level,PH, Temp, when was the last time you change water, what kind of filtration do you use
Ammonia is in the safe zone, nitrites are at 0, nitrates 10, p.h Is around 8. Temp in both tanks are 78.

And,

Are they both new set ups?

Did you add the fish all at the same time, or around the same time?

FYI, the fish in your 20 gallon tank are not compatible.
I set them up a few months ago. (July). I cycled both tanks before adding the fish as well. Also, which fish aren’t compatible? I haven’t had any issues with fish fighting or nipping at each other
 

James079

I set them up a few months ago. (July). I cycled both tanks before adding the fish as well. Also, which fish aren’t compatible? I haven’t had any issues with fish fighting or nipping at each other
Have you checked for any diseases or illnesses? They often spread rapidly in community tanks although I can't think of anything off the top of my head for it. As for the not compatible part, some fish tend to nip the fins of bettas - and other large flamboyant fish can get in fights with them, although this isn't always the case and bettas and small fish can live happily.
 

!poogs!

I set them up a few months ago. (July). I cycled both tanks before adding the fish as well. Also, which fish aren’t compatible? I haven’t had any issues with fish fighting or nipping at each other

20 is too small for an Oscar. And within a short amount of time everything in that tank would be a meal for the Oscar. First the barbs, and then the gouramis.

And the bio load from the Oscar would be hard to keep up with in 20 g of water, with company.
 

Julie Rogers

Have you checked for any diseases or illnesses? They often spread rapidly in community tanks although I can't think of anything off the top of my head for it. As for the not compatible part, some fish tend to nip the fins of bettas - and other large flamboyant fish can get in fights with them, although this isn't always the case and bettas and small fish can live happily.
I didn’t have any large finned fish while I had the bettas, but they were fine with the smaller ones that I did have! Also I don’t think there was any Illness, however one of the bettas and one of the tiger barbs lost a lot of their color before dying. /:

20 is too small for an Oscar. And within a short amount of time everything in that tank would be a meal for the Oscar. First the barbs, and then the gouramis.
What size is suitable for an Oscar? He never was mean to the others (from what I saw at least) but I will keep that in mind. Thank you
 

James079

What size is suitable for an Oscar? He never was mean to the others (from what I saw at least) but I will keep that in mind. Thank you
They need a very big tank due to the size they can grow up to, id say anywhere above 75 gallons for a decent sized Oscar. I'm not too sure what could be the issue. Are you cleaning your filter using tap water? If so that could be the reason of the sudden death. Where they fine before now?
 

!poogs!

What size is suitable for an Oscar? He never was mean to the others (from what I saw at least) but I will keep that in mind. Thank you

Couple of ways at looking at tank size for an Oscar. When they are 2 and a bit inches you can get away with a 33 gallons, but your going to have to keep getting a bigger tank to meet their requirements. I think most people will start them in at least 70 to 90 gallons, even that’s not enough over time. My personal opinion is 125 gallon is a good start, but 200 gallons plus is optimum if you want to own more than one and keep them their full life expectancy. And over filtration for Oscars is best, filtration rated at more than the size of tank.
 

Julie Rogers

They need a very big tank due to the size they can grow up to, id say anywhere above 75 gallons for a decent sized Oscar. I'm not too sure what could be the issue. Are you cleaning your filter using tap water? If so that could be the reason of the sudden death. Where they fine before now?
When I rinse it out, yes. I had been told using filtered water wasn’t the best to use. Should I use water with water conditioner when I rinse it? I hadn’t even thought of that before.

Couple of ways at looking at tank size for an Oscar. When they are 2 and a bit inches you can get away with a 33 gallons, but your going to have to keep getting a bigger tank to meet their requirements. I think most people will start them in at least 70 to 90 gallons, even that’s not enough over time. My personal opinion is 125 gallon is a good start, but 200 gallons plus is optimum if you want to own more than one and keep them their full life expectancy. And over filtration for Oscars is best, filtration rated at more than the size of tank.
Oh my. Thank you, I’ll remember that
 

James079

When I rinse it out, yes. I had been told using filtered water wasn’t the best to use. Should I use water with water conditioner when I rinse it? I hadn’t even thought of that before.
Well then I think I've found your issue. When rinsing your filter with tap water the chlorine in it kills the beneficial bacteria.
In short - This restarts your Cycle as the bacteria has to re-establish and can't handle the loads and as such they spike and kill your fish.
When cleaning your filter you should use water from your tank.
 

Julie Rogers

Well then I think I've found your issue. When rinsing your filter with tap water the chlorine in it kills the beneficial bacteria.
In short - This restarts your Cycle as the bacteria has to re-establish and can't handle the loads and as such they spike and kill your fish.
When cleaning your filter you should use water from your tank.
Noted. I will try that next time. Thank you!
 

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