recently got a new 14 litre tank

[bellaroseeee]

Hi so I recently got a new 14 litre tank and let the water run for about 2 weeks with the water conditioner in and took it for testing and it was all good. So i bought 3 guppy (male) and a fighting fish (I know stupid decision but the lady convinced me they would be fine). Anyways I had them for one day and everything was fine until i woke up the next day to realise the fighting fish had eaten part of one of my guppy tail so I took the fighter fish back and went to a proper aquarium and they suggested a dwarf gourami.

So far i have had to dwarf gourami for 5 days and everything had been fine until the past few days. All of my guppy have bits eaten off their tails and the dwarf gourami is chasing them (mainly the orange one aka the one originally eaten by the fighting fish). Two of my guppies are sulking at the bottom of the tank but do still swim around while to remaining guppy stays mainly at the top nipping at the top of the water. I feed them every morning before school and I see the guppies eat but have only seen the dwarf gourami eat once. I also know the dwarf gourami knows the food is there because he will swim straight past it. The dwarf gourami is currently ramming itself into the glass and pacing back and fourth on one the side of tank.

Please help with any information you have i would really appreciate it, it is also my first time having fish since i was quite little.

edit: i have a thermometer and build in filter with a large fake tree and i feed them tiny pellet things

 

[ZxC]

3.5 gallon tank is really only good for a single betta or some shrimp.

The tank is likely not cycled, and with that many flashy male fish in such a small tank, you'll never be able to calm the aggression.

I would try and rehome the fish and look into properly cycling the tank, and properly stocking it. Sorry if this isn't the news you wanted to hear.