if that was the case at that size no it wouldnt be over stocked look at the 1st one you should be able to tell the tank is pretty much empty give it a small group of fish on the side.No, I never gave a number. 5 adult guppies in a 30long wouldn't be overstocked, IMO, if it was filtered. I was thinking a few hundred guppy fry to become feeders for something else. In such a case, yes, overstocked, but the fish aren't going to live forever anyway, they become someone elses dinner.