Hi I had 4 blue rams 3 of which died in what I believe was an internal parasite infection (clear feces) brought in through the 4th fish. My 4th ram is alive and as happy as ever, however I think she is somehow immune to this parasite and just spreads it to others unknowingly, I only have one tank 15 gallons so quarantining right now isn't an option. I want to know when I can add more fish without hurting them.