Why do my fish keep dying in the same tank?

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100suno

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I've had at least 8 fish die here before, and all show the same symptoms. First, they get very listless and unable to keep balance then gradually they get worse. Just before they pass all of them start to curve into a C shape. I've also noticed that a crooked spine develops a bit before death. I suspect something in the tank, because the fish that move out end up fine.

my first batch of livebeares slowly started to die out all very suddenly and within short timeframes. Same exact symptoms. Moved the remaining fish out, they are ok. I bought 2 guppies and the day I moved them in they were already flashing and flicking. After a week or two both started flashing even worse and died a day or two after eachother.

Now half of my corydoras have died. Should I consider getting a new tank?

ammonia - 0 nitrite- 0 nitrate - i'm testing tomorrow ph - 8.1
 
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Also I've tried dosing melafix and gill flukes medicine, both of them didn't work at all
 
Heya, You probably have but, did you properly cycle your tank before adding the fish? It sounds like they are getting poisoned, do you use a dechlorinator for water changes and have you used chemicals or cleaning supplies other than vinegar while cleaning your tank, do you know where your plants come from and did you rinse them out well? Also when that many fish die, so fast and seemingly without cause I would absolutely start over your tank unless you find the reason and it is fixable. I recommend against using medications unless you know what the problem is you're trying to fix.

Sorry to hear about them passing on I'm sure you're doing what you can.
 
Also what is your water change schedule? Did you add any new decorations in the weeks before the issue began?
 
Any pictures and short video of the fish, and pictures of the tank?

If fish are flicking/ rubbing on objects they either have external parasites or there is something wrong with the water quality. The best treatment for external parasites is salt, poor water quality is treated with big regular water changes and gravel cleaning the substrate.

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SALT
You can add rock salt (often sold as aquarium salt), sea salt or swimming pool salt to the aquarium at the dose rate of 1 heaped tablespoon per 20 litres of water. If there is no improvement after 48 hours you can double that dose rate so there is 2 heaped tablespoons of salt per 20 litres.

If you only have livebearers (guppies, platies, swordtails, mollies), goldfish or rainbowfish in the tank you can double that dose rate, so you would add 2 heaped tablespoons per 20 litres and if there is no improvement after 48 hours, then increase it so there is a total of 4 heaped tablespoons of salt per 20 litres.

Keep the salt level like this for at least 2 weeks but no longer than 4 weeks otherwise kidney damage can occur. Kidney damage is more likely to occur in fish from soft water (tetras, Corydoras, angelfish, gouramis, loaches) that are exposed to high levels of salt for an extended period of time, and is not an issue with livebearers, rainbowfish or other salt tolerant species.

The salt will not affect the beneficial filter bacteria but the higher dose rate (4 heaped tablespoons per 20 litres) will affect some plants and some snails. The lower dose rate will not affect plants, shrimp or snails.

After you use salt and the fish have recovered, you do a 10% water change each day for a week using only fresh water that has been dechlorinated. Then do a 20% water change each day for a week. Then you can do bigger water changes after that. This dilutes the salt out of the tank slowly so it doesn't harm the fish.

If you do water changes while using salt, you need to treat the new water with salt before adding it to the tank. This will keep the salt level stable in the tank and minimise stress on the fish.
 
Heya, You probably have but, did you properly cycle your tank before adding the fish? It sounds like they are getting poisoned, do you use a dechlorinator for water changes and have you used chemicals or cleaning supplies other than vinegar while cleaning your tank, do you know where your plants come from and did you rinse them out well? Also when that many fish die, so fast and seemingly without cause I would absolutely start over your tank unless you find the reason and it is fixable. I recommend against using medications unless you know what the problem is you're trying to fix.

Sorry to hear about them passing on I'm sure you're doing what you can.
Yeah I did, I don't use any supplies when cleaning apart from de chlorinator. My plants have been in here since January, honestly I can't even remember what I did with them since a lot has happened since then.
 
Also what is your water change schedule? Did you add any new decorations in the weeks before the issue began?

I added a piece of driftwood (cleaned it with hot water before adding it) and recently a small clay tunnel which I bought online. I do 20-30% water changes per week.
 
Did you cycle your tank? Are you aware of the aquarium nitrogen cycle?
 
Did this problem start before or after the clay tunnel? I'm not sure if the clay could be leaching something into the water.

One thing to try is doing daily 75% water changes for a few days to see a) if the living fish that are showing symptoms improve or b) if it somehow changes the situation otherwise.

I also noticed in your earlier posts that you were having some difficulty with hardness etc, and I was wondering if you had gotten those parameters stabilized and if the fish you have are suited for your water hardness?

Did the salt appear to help?

If this is an ongoing issue despite the above,then the next step if you continue to suspect it is something in your tank is to take out all the decorations (and substrate depending on if it may pose a risk or not), hydrogen peroxide dip the plants,put the plants back but leave everything out of the tank while continuing to do large water changes.

Sorry that I'm no expert in this,I would recommend looking up posts that colin_t had commented on in the emergency forum with similar symptoms and see if anything there matches what you are experiencing.
 

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