Do fry tanks need filters?

One of the molly fish I just bought apparently gave birth. I didn't see it happen, I didn't know she was pregnant. Most of them must have been eaten because I only noticed them when I cleaned the gravel with my hose today and had 2 live babies in the 10 gallon container I let the water flow into. My filter had one dead one in it and when I looked up I saw a small tetra eating another fry. I've never had fry but I know they deliver more than four. I don't see anymore and my tank is 55 gallons with over 30 small fish and is pretty densely planted so I'm not uprooting the whole tank to find the rest. I put a spare heater I had in the 10 gallon container that has water from the tank (I sucked all the poop out and put in some clean water). I did crush up some flakes to a powder form because I have no idea how long they've been in the tank with no food. I don't have another filter. Do they have to have a filter?