ok i have some guppy fry and i would like to keep them as i have a 55 gallon tank with only 5 fully grown guppies, what can i do to prevent inbreeding and can they even inbreed like cats and dogs
You can't prevent inbreeding. Guppies will inbreed freely, in fact that's how most varieties are developed. As a side note you would probably get more info if you post this question in the livebearer section.