Need help

[dylanmg]

Hello, this is my first post here. My mom has a cold water tank that used to have 3 fancy goldfish, 1 comet goldfish and 3 koi fish. She added in a black koi less than a week or so. The black koi turned gray and had red gills so my mom returned him, 2 days later both kois died. After she changed her water, one koi immediately started to swim upside down and side ways and lay on the bottom of the tank, he died within minutes. The other koi did the same, but lasted overnight and died in the morning. We are not completely sure why it happened. The goldfish are completely fine. Below is more info on the tank.


65 gallon cold water tank.
Temp around the low 70s.
Tank has been running for a couple months now.
No heater, two marine land filters.
3 fancy goldfish, 1 comet goldfish, 3 kois(used to be)
Changes water everyday due to high nitrites.
She changes 70-80% of water everyday 1-2 days.
She uses 2-4x dosage of seachem prime.
She barely has any gravel, 95% is bare bottom.
She didn’t understand cycling, so she’s in the middle of a fish-in cycle.
She uses API freshwater test kit.
Ammonia 0ppm, Nitrate 10-20ppm, nitrite ranges from 0.50-2ppm, PH 7.6
She feeds her fish everyday
She feeds frozen veggies and frozen meat like blood worms, shrimp, etc.
She feeds twice a day, first time pellets, second time frozen food
She had two kois for a couple months, black koi fish for a couple days.
Swimimg erratically, no control, sideways and upside down, and lays on bottom of tank.
No fish was ill, or injured when we first got them, black koi got ill after couple days, 2 kois got sick after water change.

MORE INFO.

My mom has had trouble with the fish-in cycle. She’s been cycling for about 9 weeks but still has a dangerous amount of nitrites in her tank. It ranges from 0.50-2ppm. Past couple days it’s been 0.50. She’s put bottled bacteria, added java ferns, anubias’, swords, photos, monstera, and deliciosa, which she has grown in soil and added them in in hopes to suck in the toxins. She’s added api quick start, stability, and fritzyme 7. She got seeded filter media from a fish shop the same day the 2 kois died after the water change. After the water change, the water was cloudy. Koi died, she removed the seeded filter media and the plants she’d grown in the soil, put back her old media and changed the water. Checked parameters, nothing was out of the ordinary besides nitrites. When she changed the water the second time, the water was much clearer. Can you please help me figure out what could’ve went wrong?

 

[Aiken Drum]

What might be happening that fits your timeline is ammonia isnt an overnight killer, it tends to manifest a few weeks after there was problems with the tank. So the fact your ammonia is fine now is irrelevant, its the ammonia that was in the tank weeks ago that did the damage. Do you know what sorts of ammonia levels you saw throughout the fish in cycle?

2 other contenders.

Nitrite.

The new fish brought something with it.

Also, those are big water changes and could be causing big fluctuations in water conditions which is bad for fish. Are you temperature matching new water with the tank water? Might be better to do smaller water changes (no more than 50%) a few hours apart rather than 1 big one.

I understand you are doing your best, but that is a lot of messy fish to be doing a fish in cycle. Whatever you do, stop adding new fish until you are cycled for the ones you have now. You might also run into issues with the tank size longer term. Your tank is on the small size for when those fish get fully grown.

 

[dylanmg]

What might be happening that fits your timeline is ammonia isnt an overnight killer, it tends to manifest a few weeks after there was problems with the tank. So the fact your ammonia is fine now is irrelevant, its the ammonia that was in the tank weeks ago that did the damage. Do you know what sorts of ammonia levels you saw throughout the fish in cycle?

2 other contenders.

Nitrite.

The new fish brought something with it.

Also, those are big water changes and could be causing big fluctuations in water conditions which is bad for fish. Are you temperature matching new water with the tank water? Might be better to do smaller water changes (no more than 50%) a few hours apart rather than 1 big one.

I understand you are doing your best, but that is a lot of messy fish to be doing a fish in cycle. Whatever you do, stop adding new fish until you are cycled for the ones you have now. You might also run into issues with the tank size longer term. Your tank is on the small size for when those fish get fully grown.

Thank you very much for your helpful response, here’s what my mom has to add. She hasn’t been checking ammonia as much as nitrite, so we will focus on that. Everybody was fine for 2 months until the new koi came in, got sick, left, and then two other kois died. The death was super sudden, as soon as she finished a water change a koi immediately died, do you know what could’ve caused that?

 

[dylanmg]

Thank you very much for your helpful response, here’s what my mom has to add. She hasn’t been checking ammonia as much as nitrite, so we will focus on that. Everybody was fine for 2 months until the new koi came in, got sick, left, and then two other kois died. The death was super sudden, as soon as she finished a water change a koi immediately died, do you know what could’ve caused that?

Also, I’m not completely sure any fish showed signs of ammonia poisoning besides the black fish, can fish still die from ammonia without clear, blatant signs?