Guppy Fin Nipping!! :(

Help!!! I had just got my Guppies yesterday and put them in Platy tank (2 male guppies and 4 female guppies & 3 female Platies and 1 male platy) I had realised one of the guppies had given birth in the bag only a couple survivedead: but are thriving in my heavily planted tank. I noticed that one of my snakeskin guppies had a few cuts in it. First I thought it was fin rot but it wasn't. Then I just thought it was the tail's design, nope. Next day I check on all of them. My platies have no nipped fins but my other male guppy (which was fine yesterday) Has a few cuts in his tail fin and his top fin. I honestly don't know what to do! They always seem a little aggressive to each other like "squaring-up" to each other etc

105 Litre tank
Ammonia 0ppm
Nitrite 0ppm
Nitrate 5ppm (Stays at this usually as the plants suck up any nitrate higher)
I have a piece of wood in it that I bought, I didn't soak it though, has made a bit of tanning but I just get rid of it on my weekly water change

PLEASE HELP ASAP I AM HOPING TO BREED THESE BUT NOT WITH THIS HIGH AGGRESSION

 

My guppies nip at each other all the time. Drives me nuts. My platies usually pick on each other also but it’s more the males protecting their place with the females. The platies pick on their own kind and the guppies pick on their own kind. They seem to leave each other alone though. I only have male guppies though.

 

Unfortunately, it's what guppies do. It's normal, but if it gets too bad, then separate one from another. What ratio of males to females do you have (how many males, and how many females)?

 

Unfortunately, it's what guppies do. It's normal, but if it gets too bad, then separate one from another. What ratio of males to females do you have (how many males, and how many females)?

2 males and 4 females

 

2 males and 4 females

Okay, awesome! A lot of people get too many males for the number of females, and that can cause extra aggression.

 

But I haven't... right? Is it just normal guppy behaviour that I can't really stop? :/

 

Split tails are common with guppies. I heard a podcast with the old guppy master Stan Shubel where he talked about using Vitamin B Complex to treat split tails. I'd put a half tab into my water when hatching baby brine shrimp. I never had a split tail again.