my local pet shop sold me a load of chemicals to put in my oscar tank and nearly killed my 2 oscars. ive now done a complete water change and they are back to there normal nutty ways,,, but my tiger has hole in the head but seams like a scar, can it get worse and should i treat it, thanks sylvie

Firstly welcome to our community

Glad to hear that your Oscar didn't die.

The first thing I would ask you to do is test your water for ammonia, nitrite, nitrate and pH.

I can't really help you much without seeing your Oscar, so if you can post a photograph them please do. Once we can have a look at your fish, will be easier to determine what your situation is.

while waiting for the picture as our basis, just keep an eye on water
parameter. pristine water is the best defense in any fish illnesses.
kindly give a mild dose of salt in your tank to enhance oxygenation.

hi thankyou for your help ive enclosed a photo,not sure if you can see it very clearly but i do know its called hole in the head.ive had fish for as long as i can remember and my dad owned a tropical fish shop in the 70s,but hes ill now and dosnt remember how to treat diseases but he did manage to tell me to salt the water. he also tells me not to put in chemicals in the water but i suppose in the 70s the tap water wasnt so poluted.anyway ive done the water change and things are looking good, but how often would you say i should do a partial water change?the photo won load ill keep trying

assuming that your oscar has hith the best way to treat it is with pristine water. ammonia 0 nitrites 0 and niitrates lower than 20. test your water fro nitrates and when they reach the 20 mark do a partial water change.
keep doing this until the holes are healed and withluck there wont be any scarring.
remember that it takes a while to fully cure hith so be patient and keep the water in good condition.

thanks paul.I need to buy a test kit,what is the best one to buy.ive honestly never had to test the water in any of my tanks.maybe its the polution in the tap water these days.thanks again sylvie