Filter reccomendation for a quarantine tank

[Kovenant]

Hey guys I have 20 gallon quarantine tank, today I noticed it brown/yellow coloration. Any filter reccomendation?

 

[Sharkbait19]

I use a sponge filter and a top fin hang on back for mine. Doesn’t need to be fancy, and this does the trick. The hob is nice because it allows you to put carbon in there when done with meds.

 

[Spare time]

Hey guys I have 20 gallon quarantine tank, today I noticed it brown/yellow coloration. Any filter reccomendation?

Are you running medicines?