Is it a froglet ot toadlet?

Hello i live in the uk and i have a froglet/toadlet, it is black with a speckled belly and is the size of a little finger-nail. The other tadpoles are brown patched and don't seem to have any speckles but are about 4 cm including tail. I got them frog a big lake in leeds and they were all at the side sucking algae, i wan to know if they are frogs (rana temporaria) or toads (bufo bufo).