Sorry. I realize my last post wasn't exactly helpful.
In the meantime if you test your water and keep the nitrates below 40 (0 ammonia and nitrites of course. If tank is not cycled keep those perimeters below .25) by doing water changes they should be fine. Comets are hardy fish, so if you check your water daily and do water changes they should be fine for now.
Comets will get about a eight inches to foot long (longer with some strains), btw, which is why I suggest a pond.