Spawn to Tadpole

When i popped to my allotment to water my seedlings, which are doing great, see pictures, i had a sneaky look at my pond to see how the frog spawn was doing and noticed they had developed little tails.
It wont be long before they are big enough to hatch and start swimming around.
Apparently they will eat soggy lettuce until they develop legs then they become meat eaters where ill need to provide some sort of meat or they will start to eat each other...