You overdosed the tank.
Common symptoms of Levamisole poisoning in fish:
fish become nervous and skittish
breath heavily
die
Treatment, do a huge water change and gravel clean the substrate.
Increase aeration/ surface turbulence whenever using medications in tanks.
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Before you treat an aquarium, do the following.
Work out the volume of water in the tank:
measure length x width x height in cm.
divide by 1000.
= volume in litres.
When you measure the height, measure from the top of the substrate to the top of the water level.
If you have big rocks or driftwood in the tank, remove these before measuring the height of the water level so you get a more accurate water volume.
You can use a permanent marker to draw a line on the tank at the water level and put down how many litres are in the tank at that level.
There is a calculator/ converter in the "FishForum.net Calculator" under "Useful Links" at the bottom of this page that will let you convert litres to gallons if you need it.
Remove carbon from the filter before treating with chemicals or it will adsorb the medication and stop it working. You do not need to remove the carbon if you use salt.
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When treating fish for worms, treat the tank once a week for 3-4 weeks.
Do a 75% water change and gravel clean the substrate 24-48 hours after treatment.
Clean the filter after each treatment. Wash filter media in a bucket of tank water and re-use the media. Tip the bucket of dirty water on the lawn.
Section 3 of the following link has more information about deworming fish.
Fish do a stringy white poop for several reasons. 1) Internal Bacterial Infections causes the fish to stop eating, swell up like a balloon, breath heavily at the surface or near a filter outlet, do stringy white poop, and die within 24-48 hours of showing these symptoms. This cannot normally be...
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