HELP! My Fish Keep Dying ?!

[FishAreFriends17]

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.

I actually wondered this myself, because it all started happening after we got that new filter! It’s a fluval 110 which has great reviews and that was the same filter we had before it broke. But maybe something is just off with the filter?

 

[FishAreFriends17]

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.

Okay I’m an idiot, just talked to my fiancé. We do use liquid haha. I guess I just really don’t know what I’m talking about. ??‍??‍

 

[Mick85]

If you didn't swap the media over from the old filter to the new one and didn't add an ammonia source to start the cycle on the new set up then your tank would not be cycled. Also get a liquid test kit as the paper strips are pretty useless.

 

[FishAreFriends17]

If you didn't swap the media over from the old filter to the new one and didn't add an ammonia source to start the cycle on the new set up then your tank would not be cycled. Also get a liquid test kit as the paper strips are pretty useless.

Actually, it is liquid we use. I guess I was confused about that because you compare the colors to a strip but when I told my fiancé he laughed at me and said we do use liquid. My bad. Anyway, yeah I am totally getting that we may have wiped the beneficial bacteria out of our tank but if that was the case wouldn’t the ammonia be spiking? I guess that’s where I’m getting confused.

 

[Colin_T]

What sort of fish are in the tank and what ones are dying?

Any chance of pictures and video of the fish and the tank?
Make sure the pictures are in focus and don't have any horrible weird coloured lights on the tank.

If the video is too big for this website, post it on YouTube and copy & paste the link here. We can view it at YouTube. If you are using a mobile phone to take the video, have the phone horizontal so the video takes up the entire screen. If you have the phone vertical, you get video in the middle and black on either side.

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How often do you do water changes and how much do you change?
Do you gravel clean the substrate when you do a water change?
Do you dechlorinate the new water before adding it to the tank?

What sort of filter do you have?
How often and how do you clean the filter?
What is the nitrate, pH & GH (in numbers)?
You can contact the water company via phone or website for the GH.

Do you add plant fertilisers, supplements or anything else to the tank?

Have you treated the fish with anything?

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Never buy any fish out of a tank if there is sick fish in that tank. If one fish has a disease, they all have the disease.

All new fish should be quarantined for at least 2 (preferably 4) weeks before being added to an established display tank. Obviously this second lot of fish were put into a new tank so they didn't need quarantining, but if the fish lot had been, then most of your other fishes would probably be ok.

 

[AdoraBelle Dearheart]

I just tested the water again today. I’m sorry, I’m just confused by it all.

Okay I’m an idiot, just talked to my fiancé. We do use liquid haha. I guess I just really don’t know what I’m talking about. ??‍??‍

I'm a little confused now too. You said you tested the water, but you didn't know what type of kit you use?

Which brand of kit are you using? Because there can be some user error when it comes to doing the tests, things that the instructions aren't always very clear about. Do you shake the nitrate bottle very thoroughly before each test? Because it really needs shaking, banging against a table, throwing around, and shaking some more for a full thirty seconds or more before adding the second test solution, then at least a full minute shaking of the tube before leaving it for five minutes and reading the result. I even stand in front of a clock to do this because thirty seconds feels like a long time when you're shaking away! But it's too easy to get inaccurate results, as the test solution settles between uses.

If you didn't swap the media over from the old filter to the new one and didn't add an ammonia source to start the cycle on the new set up then your tank would not be cycled. Also get a liquid test kit as the paper strips are pretty useless.

This ^^^. If you threw out the old filter including all the media, replaced substrate and everything, then just left the tank running for a fortnight without adding any source of bacteria or ammonia, it isn't cycled. Something isn't adding up here. Even if some beneficial bacteria remained on some pieces of decor or plants, that might just be enough to begin a cycle for you, but it would not be enough to handle the bioload of you going out and buying all new fish and adding them to the tank without ammonia and nitrite spikes.

How often were you testing the water after adding new fish, and how often were you doing water changes/at what volume? How many fish of what species did you add?

 

[mrsjoannh13]

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?

It was the weirdest thing. I did rinse it out in filtered water when I was setting it up. Really don't know what the deal was but all 6 fish were at the top gasping for air. I turned up the flow rate and waited a while... same behavior. Replaced it out with the old filter I was using before and within minutes the fish were fine.

 

[Malawif@n]

it does sound odd, personally speaking wouldn’t use test strips, invest in a master test kit more accurate. I agree that with changing all the substrate and replacing the old filter without adding old filter media to new filter would have removed almost all of the beneficial Bactria and even if there were some left it wouldn’t survive. It sounds like your tank is cycling all over again and it’s probably why your fish are dying. Using tap water to clean filter or even adding untreated tap water for water changes will kill beneficial Bactria. I’m no expert by any means but I have researched a lot in the past and this has happened before sounds to me like your tank is cycling all over again. If indeed your tank is cycling Treat water with seachem prime it binds ammonia and converts it to ammonium which beneficial Bactria can feed on, seachem says to use once every 48 hours or when doing water changes as it’s also a dechlorinator. You can use seachem stability which is Bactria that should help.