I'm not trying to mean, but if as you say in your "for sale" thread that one of your Oscars have HTH and you think the other may be getting it too, why are you even considering any new fish. You need to take care of what you have now. You say you care about your fish, then put them first. Treat the HTH then either upgrade your filter, or the w/c. If you can't do it for whatever reason (the grumpy granny or ?) then get rid of the Oscars and don't add anything else until you can properly take care of what you have. I understand that when you make all these threads saying different things and sometimes the exact opposite your are using this forum as a sounding board to help you make the best decision and your mind is jumping back and forth, but in the end, you are the one that has to make the choice and then stick with it. If you need to, write it down on a piece of paper the reasons to keep your fish and the reasons not to, in the situation you are telling us about I'm sure you'll figure out the right thing to do for your fish.
The one thing you need to do right away is treat the tank, the poor fish are suffering with HTH and they need to be treated.
