Planted Aquarium

[timmystood]

And ive already decided to leave singray filter in as my sister has the same tank and she hasn't had any problems, what do you mean by dangerous tho?

Several reports of then running a current through the water and killing the fish and also injuring the user. A huge (and I mean massive) amount of them have already been recalled. Hopefully, the fact you still have it means that it is in the 'safe' batch.
Personally, I also find them very poor at actually filtering the water and they don't have much room for biological filter growth.