a dime size white spot / hole

Question
"I have a Black and Orange (Tiger) Oscar and an yellow and
orange or Lemon Oscar,they share a 55gal long with a bakers dozen of inch long - Cone snails. 2 new 20-30gal submersible tank heaters, half of tank has an under-gravel filter powered by an  Elite 803 air pump n stone, and 1 Penguin 330 Dual flow filtration pump(330 filters with charcoal changed every 2-3 weeks needed or not).They are hand-size. The Tiger has a white hole  about the size of a dime above and behind the left gill slit with what looks like long same color hairs or fuzz about 1/ 8th of an inch. Started out as a spot and in about a week and a half has become a hole. I have been doing 10% water changes every 3rd day. what do you think?

Answer
Hi Ulfhednar,

Your Oscar sounds like he's got Hole In Head, or a parasitic infection.

I recommend dosing his whole aquarium with PraziPro and then doing a 50% water change after a few days, and for the following week, 10% water changes every 2 days.

This should cure the parasitic issue.  He could also have Hole In Head.

The hole could be the beginning of HIH, but if it is Hole In the Head, it will require a treatment with Prazipro also.

If you need to post a followup, please send me a photo so I can see this hole up close to be 100% sure.  It's very hard to diagnose by description.

Thanks!

Happy fish-keeping and I will cross fingers for his recovery.