I have read that they should have another with them...I had one alone for a few weeks and it seemed fine though. I bought the other just because it made me feel better for him to have a friend. I have 2 in an Aqueon 4 gallon tank. HTH I think they have finally reached some type of maturity level because I have caught them "practicing" twice now. Well....he is practicing...she is throwing him off. lol