If you really want to know what's going into your pond it is quite important to be able to tell forage fish species apart. As has been shown, some fish farms have contaminated fish stocks. I've been breeding and studying mosquitofish since I was 8. I can spot one in a school of 100 FHM...
Notice the fish I have labeled as mosquitofish. They are all smaller than average. Makes sense, as mosquitofish max out in size way smaller than FHM, whether wild colored or rosy. Also notice to the far left the normal or wild colored FHM in the picture. Notice the brown color, not the greenish color the mosquitofish have. Again, notice how all the mosquitofish are right at the surface. Again, they are surface fish unlike the FHM which are not. The only reason why some FHM are at the surface are the cramped conditions of the cooler and the gulping due to lack of DO. Last, notice how none of the fish I have labeled as mosquitofish have their mouths open to gulp air although they are at the surface unlike many of the rosy reds. This is because mosquitofish are even more low DO tolerant than FHM.
A cut of the above picture... Notice the larger fish that is contested, notice the faint yellow oval spots behind the eyes. Notice the other three are very small. If you look at the whole picture they are way smaller than the average fish again this makes sense since mosquitofish are smaller than FHM.
Here is a picture of both wild colored and rosy reds together. As labeled, notice the lack of yellowish oval dots behind the eyes. Also notice the browner color as compared to the mosquitofish which are greenish. Also notice the average size of the wild colored fish is the same as the rosy indicating they are in fact the same species and not different species.
Two pictures of wild mosquitofish, notice the yellowish oval spots behind their eyes...
