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Aquarium Advice Newbie
Dec 21, 2023
Hello fish community I am a keeper of 7 fish and 4 of them have now died.

What has happened is I recently got a new tank to upgrade from my older smaller one.
The new tank upgrade was a second hand Jewel tank thats 80l and it started to leak after about a week of me having it.

So I bought the "BETTA*Clear Aquarium silicone for sealing and repairs" to reseal the tank.
After using this silicone, sealing the tank correctly and leaving it to cure for longer than recommended time I decided to add my fish back into the aquarium.

After I had done this my fish all started to decline in health. They stopped eating, couldn't breathe in the water and most of them have died and I'm absolutely devastated.

I wiped down the aquarium before reintroducing my fish into the tank after sealing it so I cant understand why this is happening especially because I used a fish safe sillicone and followed all correct directions and yet now 4 of my fish have passed away.

Does anyone know the issue? I have been doing water changes since Ive noticed the issue and that has improved the health of a few of my fish but unfortunately it was too late for some of them.

Please please please help me or tell me what I could do to stop this besides water changes as im already doing that. Also to note before I noticed the tank started leaking my fish were living perfectly happily in the tank and only after I sealed it did this start happening.

What I did exactly was move my fish out of the tank and put them in a holding tank while the new one was getting repaired.

Then I dried and repaired the new tank and left it to cure for longer than recommended time. My father also did all the sealing with the sillicone as hes experienced for many years in using it.

After it dried I wiped the tank down with a wet cloth, filled the tank back up and reintroduced my fish and thats when the issue started to happen.

Please help me.
Jewel aquariums tend to have a built in filtration system. Is this tank that type? If so did you cycle the tank before moving the fish?
Jewel aquariums tend to have a built in filtration system. Is this tank that type? If so did you cycle the tank before moving the fish?

This one is just your average tank its got nothing built into it but I dont have anything to cycle my tank and I haven't done that before with my fish and they have thrived since they grow in size have healthy colours ect but after I seemed to have resealed my tank they have started passing away
You used an aquarium safe sealant and sealed the tank in accordance with the maunfacturers recommendations. Your fish are dying because the tank wasn't cycled. Do you know how to cycle a tank?

7 fish in a 80 litre uncycled tank is a lot and will be causing water quality issues. Short term you should be doing 50% water changes every day until your cycle starts to establish.
Thing is tho, I added them to my tank before it started leaking and it wasn't cycled because I cannot afford things like conditioners ect for tank cycling and they were thriving as normal and living happily but once I resealed the tank thats when they started dying even though I followed all instructions and they were being held in there previous tank while I was repairing the new one

Ammonia toxicity takes a while to affect fish. The ammonia has to build up over time to toxic levels.

What we know is that you used an aquarium safe sealant and you used in accordance with manufacturers instructions. We can rule that out.

We know that you didnt cycle the new tank before adding your fish and we know you didnt follow a safe cycling process after adding your fish. We know that with the number of fish you added into an uncycled tank of that size, ammonia will start to build. Your fish started to see ill effects in keeping with water quality issues that you would expect to see in an uncycled tank. Some fish died and you did water changes and things improved. This is what we would expect to see.

I cant be 100% sure this is the cause, but unless you are failing to tell us something im 99% certain.

Whatever you do, your tank will cycle naturally. There are measures you can take to do this relatively safely to your fishes health.

The lack of a water conditioner is concerning though. If you have kept fish in the past without a conditioner then it may be your water supply isnt treated with chlorine/ chloramine or you are dealing with the treatment in another way. If so more details would be helpful.

What filtration are you using? Did you transfer this filtration from your old tank to the new or did it come with your used tank?

Do you know your water parameters? pH, ammonia, nitrite and nitrate?
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