Like I said, hes in a 55g alone with a marineland C-220 and a ac70. The water gets tested once a week before I do my waterchange and it always reads 0 ammonia 0 nitrite 5-15 nitrate. As for food, he eats Hikari pellets so idk how he got this.
I think I said it was the best way to control them, but not necessarily to prevent them. some would argue that parasites are always present in some form. you cannot predict when parasite problems may show up.
to take it to the next level, many people run UV lights on their tanks as well; I run UVs on my 30 and 90G tanks. I should have mentioned UV earlier, but it won't help your current situation anyway.
oh, and I see the pea suggestion, and I think it's worth trying, but it also might be a good idea (in future) to mix up the fish's diet a bit. if you feed Hikari as a staple food, that's fine, but you could also mix in some other foods and treats to give him a mixed diet. maybe not necessary, but possibly helpful