I think my fish have/had Ich or fin rot


Reefing newb
My Royal grammar and chalk white goby had torn and ragged fins the other week, In a couple of days both were fully healed and they continue to eat well, even the chalk white goby has actually learnt to eat the dried granule fish food. Was it fin rot? Will it happen again?

My Royal Grammar however also had small white spherical spots all over its tale and head. These I think are gone but it continues to flick itself against surfaces from time to time. I had just noticed recently an extraordinary event where the Royal Grammar allowed the Peppermint shrimp (previously aggressive to the shrimp) to mount it seemingly performing some kind of manicure. I'm think it was eating the parasite (if it was/is Ich) hopefully not eating the fish....What was going on?

Their immune systems seem to be stable but I don't want them continually getting sick. I think it might be water. I'm planning a water change as I noticed in a recent test Nitrates presence was positive. I want to do a full change to RODI. Can anyone give me any pointers on how to conduct that conversion without stressing the fish?

Some insight with any of the above would be great

Starting to mix up your saltwater using RODI will not stress the fish. It will just achieve what we all want; Eliminating toxins and/or nutrients from entering your system that may have been coming from the tap. Just keep the tank nice and stable on salinity and temperature, and feed your fish some quality frozen food. Some people use garlic drops and vitamin drops in the frozen food to support immunity as well. Good luck!