However, if you have gravel, I would definately recommend siphoning by disturbing the gravel. Of course, you can't do this very easily with the frogs in the tank since they tend to either be overly curious or stressed to the max. I know some people are all worried about nets, but this is the easiest way to transfer them. You should change the filter per the manufacturers instructions because if you don't, the beneficial bacteria won't mean much when the filter itself is shot. Keep monitoring the tank too.
Tanks do mini cycles all the time.
Overtime, this will lead to toxic levels of amonia that are completely unrelated to your tank's normal cycling. It is a matter of preference though. However, if you have gravel, I would definately recommend siphoning by disturbing the gravel. Of course, you can't do this very easily with the frogs in the tank since they tend to either be overly curious or stressed to the max. I know some people are all worried about nets, but this is the easiest way to transfer them.