Re: So, you want a reason to not mix species?
That is a very irresponsible post. This information is not based on any facts or experience and is only being posted to further stir the pot on the topic of mixing species. It is post like this that hurt this hobby. Posting inaccurate data based on your belief instead of actual experience with the subject.
You may be of the opinion that mixed tanks are difficult but that is simply not the case(this is based on almost 10 years keeping mixed tanks and assisting others with the setup and maintanence of their mixed tanks). What you have shown is that aggression can happen in a single species tank and happens more then one would think because almost every tank is setup with unsexed juveniles. The wrestling behavior you witnessed is a normal(as stated by the previos two posters) function of how frogs interact to establish a hierachy within a group. It is when this aggression becomes excessive that it needs to be addressed.
Also, it is not recommended to setup a mixed species tank or keep a group of leuc's in a small enclosure, as you stated.
Last edited by Jellyman; 05-14-2009 at 02:06 PM.