I need some urgent assistance please. I came home from work on Thurdsay evening to find three of my discus gasping at the top of the water looking very unwell. I immediately did a large water change and put in some discus vitamins. My husband then did another small water change Friday morning and then I did a 3/4 tank change on Friday evening. By this stage I was very concerned as one was only breathing from one gill and all were covered with excess mucus. I thought that it could well be gill flukes. I went to my local supplier who suggested Formalin. I got home on Saturday and moved the three sick discus to my small quartine tank where I treated them (1 ml for 70 litres)
By Sunday morning two had died (the last one died later that morning) When I turned on the lights on my main tank I found that the remaining fish all had cloudy eyes and my ghost knife fish was laying on the bottom of the tank. I then went to another fish supplier who suggested Malachite green with the formalin and feeding the discus with beefheart mixed with garlic and chilli juice (he has been breeding for 15 years)
We moved the fish to a quarantine tank for a salt bath and then back to the main tank where we treated it with 7ml Formalin and 5ml Malachite Green (Have since learned that this will kill all my filter media but c'est la vie). Have removed carbon and turned off UV light.
The ghost knife fish was dead this morning. The fish are swimming better today but all have cloudy eyes (almost like catarachs) and I have noticed that two have frayed tail fins.
My tank spec is
450 litres (uk)
Ammonia 0
Nitrite 0
Nitrate 0
Filtering with x 2 Fluval 305's
UV sterliser
3/4 RO Water to 1/4 treated tap water (ph of 7)
Temp at 30 degrees

The reason for all of this was a new purchase two weeks ago which I didn't quarantine first(!) I now only have six fish left in my massive tank and worried a) How long to leave them in the formalin/malachite solution b) Are they suffering with a secondary infection. Can anyone help me

Many Thanks to all

Nicky

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