I had one (named Waldo, because you always had to search for him), but I traded him back in after reading a few of the war stories on here about how they totally crashed some tanks. Seems there are some types that are okay, and others...very, very bad if they die because they will release a toxic discharge into your tank killing everything. The problem is, I could never get a clear conclusion as to which is which...You don't know until it happens. So, I wasn't willing to take the risk any longer. One common response that I did hear was that the more colorful one's caused the most problems. Mine was a dark brownish green, but again, not worth the risk.