I have a real guppy pest in my 18.5 gal
...so I went to my lfs
, and asked for a fish that will diminish my guppy population.
The owner suggested some fish, but I stopped him when we got to a tank with killies. They were good as well he said. So I took home some Aplocheilus lineatus.
They have been in the tank for a couple of hours now, and I've seen the male (I think the goldish one is the male) go for a little guppy a couple of times. He hangs perfectly still, and then when a little guppy swims past, he shoots forward so fast I have to look for him again between my plants (my eyes can't follow his speed!)
Here's some pics: