HELP! My Fish Keep Dying ?!

[FishAreFriends17]

So , my fiancé and I have a 65 Gallon Fresh Water Aquarium. On January 16th we got some new fish for it at our usual fish place. Well, when we bought the Corys they were in a tank with these tetras and the guy at the store was like “I just want to warn you, we just got a shipment of these tetras in and they keep dying. The Corys have been fine, but since they’re housed in the same tank I wanted to warn you.” But we said it’s okay and then bought them anyway. Well, the next day we were messing with the fish tank and accidentally broke the filter ??‍, and had to get a replacement.

Okay, so now flash forward a couple of days later and we slowly start seeing fish dying. One by one. We’d wake up and another fish would be dead. It started with a lot of the new fish we bought but then it started happening to our older fish who we’ve had FOREVER as well. So, we did a complete take down of the tank. Cleaned it. Put all new substrate. We did put some of the same plants and aquarium wood back into the tank. But everything else was fresh. We gave the tank two weeks to cycle AND checked the water parameters and although the pH was a little high around 7.8, everything else looked good.

Sooooo, last Saturday (March 6th) we went back to the fish store and bought all new fish for the tank. Now, they’re dying again. Slowly. One by one. The water quality is fine (I mean some of the fish are even breeding) but we keep finding dead fish. Also, twice now we’ve seen a fish gulping at the top of the water, acting strange, and then dying. I’m not sure if it’s a lack of oxygenation. I mean the filter is working I see water flowing out and bubbles in the water. Or if it’s something else. Could the filter not be working properly!!? Ugh, we are just getting so frustrated because we can’t figure out what’s going on ?. Any ideas/ guidance would be so helpful!!!

 

[UnknownFishies]

@Colin_T

 

[UnknownFishies]

Any noticeable changes with them? White spots? Are they eating? White Stringy Poop?

 

[FishAreFriends17]

Yeah. They’re eating normal. No white spots or white stringy poop . Everything looks okay and then they’re just dead. The only strange behavior I noticed was with the two fish that were like gulping at the top of the aquarium.

 

[UnknownFishies]

Hmm... that sounds like ammonia or nitrite presence but you said there wasn’t any. Did the fish store clerk give any other information about the fish?

 

[FishAreFriends17]

Both the Nitrite and Ammonia are measuring 0. It’s so odd. He didn’t say anything more about the dying tetras that day.

 

[kwi]

When you got your new filter did you transfer the old filter media to it?
How did you cycle the tank in two weeks?
How are you testing the water? Liquid tests or strips?

 

[FishAreFriends17]

My fiancé says he can’t remember if he transferred the old media but I’m guessing he didn’t. Once all the fish died from the old setup we put new substrate and water in the tank and then just let the water run for two weeks. Then we checked the water parameters and everything looked good so we bought some fish. I’m testing the water issuing strips.

 

[kwi]

Sorry to say the water would look good as there was no fish waste to feed the bacteria that we rely on to keep the tank healthy, if no ammonia gets into the tank at all the no nitrites or nitrates will appear bar those that are in the tap water. Changing everything in the tank has removed all the bacteria you had before.
There is an article here that explains the nitrogen cycle and how to do a fishless cycle. And a few youtube videos that are very good at explainingthe Nitrogen cycle.
You are now doing a fish in cycle, keep the tank minimally stocked and test for ammonia and nitrite every day, preferably using a liquid test, the master test kit from API is good value when calculating a cost per test, especially compared to strips, which aren't considered too accurate anyway.
You'll need to do a large water change evertime you get a reading above 0 for ammonia or nitrite, and large is over 75% of the volume. This will be a hassle for a while but will eventually settle once the bacteria colonies have built up enough to do the job.
The plants will help a bit with the nitrogen cycle, especially if they are fast growing varieties.
@AilyNC had to go through a fish in cycle so maybe can offer some help.

 

[HoldenOn]

Sorry to say the water would look good as there was no fish waste to feed the bacteria that we rely on to keep the tank healthy, if no ammonia gets into the tank at all the no nitrites or nitrates will appear bar those that are in the tap water. Changing everything in the tank has removed all the bacteria you had before.
There is an article here that explains the nitrogen cycle and how to do a fishless cycle. And a few youtube videos that are very good at explainingthe Nitrogen cycle.
You are now doing a fish in cycle, keep the tank minimally stocked and test for ammonia and nitrite every day, preferably using a liquid test, the master test kit from API is good value when calculating a cost per test, especially compared to strips, which aren't considered too accurate anyway.
You'll need to do a large water change evertime you get a reading above 0 for ammonia or nitrite, and large is over 75% of the volume. This will be a hassle for a while but will eventually settle once the bacteria colonies have built up enough to do the job.
The plants will help a bit with the nitrogen cycle, especially if they are fast growing varieties.
@AilyNC had to go through a fish in cycle so maybe can offer some help.

Daily 50% water changes with prime. That's what I did.

 

[kwi]

Daily 50% water changes with prime. That's what I did.

I keep forgetting about prime as I've never used it, but then I've been told to stay clear of it during cycles as it binds all the ammonia and the bacteria don't get their lunch.
(As a caveat I've never looked at this claim closely as I never use prime.)

 

[mrsjoannh13]

Just throwing this out there... I got a new tank kit (cheap Topfin brand) and there was something wrong with the HOB filter that came with it. I set it up to move my fish into (the new tank was 20g and the previous tank only 10g). I transferred over the established media from the cycled tank and filter. Within an hour of going in the new tank my fish were all gulping air at the top of the tank frantically. The filter was working from the standpoint of pulling water in the intake and I could see the water coming out of the filter back into the tank. So it was 'operational'. But something was off with the oxygen level in the tank. I have no idea why. I lost 1 fish and almost lost another. Luckily I had some spare HOB filters on hand and as soon as I put the new filters on the tank the fish were fine. My water had no ammonia or nitrite - all the parameters were fine. It was the filter. So if you are seeing them gasping for air and you don't have ammonia in the tank consider another filter.

 

[FishAreFriends17]

Hey! Thank you so much for the advice.
So, what you are saying is you believe there is not enough beneficial bacteria in the tank, correct? I guess, I am just confused as to why the Nitrite and Ammonia levels are reading 0 and the Nitrate is at 20ppm. Unless these strips aren’t accurate? I just tested the water again today. I’m sorry, I’m just confused by it all. It would seem to me if the fish are dying related to the lack of beneficial bacteria the ammonia or nitrite levels would be elevated. Thanks again for your guidance!

 

[kwi]

Just throwing this out there... I got a new tank kit (cheap Topfin brand) and there was something wrong with the HOB filter that came with it. I set it up to move my fish into (the new tank was 20g and the previous tank only 10g). I transferred over the established media from the cycled tank and filter. Within an hour of going in the new tank my fish were all gulping air at the top of the tank frantically. The filter was working from the standpoint of pulling water in the intake and I could see the water coming out of the filter back into the tank. So it was 'operational'. But something was off with the oxygen level in the tank. I have no idea why. I lost 1 fish and almost lost another. Luckily I had some spare HOB filters on hand and as soon as I put the new filters on the tank the fish were fine. My water had no ammonia or nitrite - all the parameters were fine. It was the filter. So if you are seeing them gasping for air and you don't have ammonia in the tank consider another filter.

That's a strange one as oxygen enters the tank via the water surface, the filter agitating the surface helps improve this by giving a bigger surface area, as does an airstone. I wonder was there something toxic in the new filter?

 

[kwi]

Hey! Thank you so much for the advice.
So, what you are saying is you believe there is not enough beneficial bacteria in the tank, correct? I guess, I am just confused as to why the Nitrite and Ammonia levels are reading 0 and the Nitrate is at 20ppm. Unless these strips aren’t accurate? I just tested the water again today. I’m sorry, I’m just confused by it all. It would seem to me if the fish are dying related to the lack of beneficial bacteria the ammonia or nitrite levels would be elevated. Thanks again for your guidance!

Your levels could be elevated, strips are known to be wildly innacurate, hence the recomendation of getting a liquid test kit.
Do you know your tap/source water nitrate levels? 20ppm is not unheard of.