They're actually for fish to lay their eggs in but if you get creative, you can make them so they aren't as dense and the fry can hide in them. One website suggested tying them to corks so they float better.
Edit: Or see if you can find Java Moss. It might cost about $6 but it does work great to hide fry in.
Welp, I'm going to take a short nap. I've got to make another pet store run later to pick up some filter media (so mad I didn't notice I was out before I went to the pet store this morning). I'll be off now.
Congrats Neil, hope you have fun with it! Actually, I think this whole experience turned out for the best, dwarf puffers need cycled tanks, so I might as well cycle it now anyway. And I come away knowing never to put a betta in with less than 3 platies. And I think I'll get the Java Moss, I cant tie or sow anything :D for a fish-in cycle on a 5 gallon, 1 50% just water and 1 50% cleaning gravel, decorations, and such weekly is good, right?
Diablo, yeah. Maybe even just 1 50% a week with gravel. The idea is to leave enough ammonia in there for the bacteria to grow. If you have an ammonia test kit, test frequently and change the water when the ammonia gets to about .5. I believe .25 is when the fish start to feel discomfort.
When I tried to cycle my 10g the very first time, I was always worried my betta was suffering so I changed the water like every other day. Never was enough ammonia to cycle with. Oops.
And did you know puffers need to eat things that are hard, like things with shells? If they don't, their teeth can get too long. Wow. I'm not sure about dwarf puffers. Maybe that only applies to the bigger puffer fish.