Bullfrogs take 2 years to mature from egg to adult. The tadpoles will be 2"-3" long and the body will be about 1/2"-3/4" across. Bullfrog tadpoles are more of a brown color, if you're seeing a lot of black tadpoles, those are most likely toad tadpoles.

Do you have adult bullfrogs in the pond or close by now?

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3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).