yup. if you have a very matured tank with lush algae growth, you might not need to feed them but they won't grow as fast.
if you feed them, they grow very quickly.
also if you have alot of pod eaters in your tank like leopard wrasse, mandains, pipe fish, seahorse etc, the population will decrease. not all fish eat pods. one very famous and BAD example is ALL WRASSE eat pods. this is so untrue i don't even know where to begin. fairy and flasher wrasses do not hunt for pods on the rocks. they are open water planktonic feeders. so ensuring you know what fish eat wat is good and make sure you don't overcrowd the number of pod eating fish. otherwise ur pods cannot grow.
you need to strike a balance where pod population is faster than pod decimation. to achieve that, make sure you have very little fish that consume pods and this will allow time for pods to grow.
for example in my 183 gallon tank. assuming the only pod eater is my pipefish, i probably don't need to do anything forever and the pods will populate faster than that one pipefish could finish.