Anyone know how long it takes to cycle with a fish? I have a 20 gallon I'm making a tropical tank, and I was looking ALL OVER for freaking Endlers Livebearers but NO ONE had any! So I got a medium sized feeder goldfish. If it lives, well, I'll just make a 10 gallon tropical tank.

You know, you don't have to use Endler's Livebearers to cycle a tank. I used Glowfish Danios to cycle my tank, and they're still just fine. It usually takes about a month to cycle a tank. If you can't find a fish more suitable to use then a goldfish, try fishless cycling. That's how I cycled my 30 tank with my two goldfish in it, and it's much easier to do because you don't have to clean the tank, feed fish, or take the risk of ammonia or nitrites harming the fish during cycling. Hope this helps!

I can't do fishless, because I won't be there for good until about the 20th when school starts. For now, the little orange and white fishy is there with a 7 day block feeder, and a filter. I forgot to pack my airpump and air stone. I hope it's alright. I'm paranoid about leaving it there by itself for so long.

From the time when you add the fish, it can take a month to perhaps 3 months. Cooler tanks take longer to cycle.