For a good example of the drawbacks of very specialized animal sites, check out this one.
There is too little traffic to keep people coming back -- and I guarantee you that the number of V.exanthematicus keepers will be substantially more than those keeping V.niloctus.
That being said, if you do go ahead you will do well to pick better forum software. Whatever one they are using isn't nearly as advanced as the one used for ssnakess.com, arachnopets etc. At the very least, the format here is workable. If, on the other hand, you realize that about the only thing you can do with such a specialized topic is create a board focused on community rather than information, then you might want to consider a listserve. Easier to setup and you can just use it to communicate between "friends."