Flagfish, I had a frontoza in a 10 gallon tank. It could be said because it can get over a foot it was bad, however, the fish was less than one inch, and only intended to be there a month or so. Assuming you will get a larger tank for them, it is not a problem if they are still small. Given 2 6" fish in your tank i would probably yell and scream. However if they are still young/small (and you really are getting them a bigger tank SOON) i would tell you to base your WCs on nitrates tests. If you can go 2 weeks with nitrate levels below 20 ppm, I say go for it.