You should be able to tell by a spot on the anal fin. If it has a spot then it is a male.
55 Gallon-two clown knifefish, chocolate pleco
46 Gallon Bow Front-Planted-swords, java fern and African cichlids, sail fin pleco
29 Gallon-black ghost knifefish, bristlenose pleco
10 gallon-brackish, figure-eight puffer, knight goby