I am a compleeeeete beginner. Emergency Situation. There is a lake near my house. Mysteriously, small channel catfish of 8-11 inches appeared. They end up getting eaten but that is disturbing the ecosystem. Some fishermen and fishsellers got them out and are selling them with other, bigger(~20"), catfish from a different ecosystem. I bought one a month ago when all this started. Now the sellers are reauesting if I could house these fish till they reach 15" at the least so they are not as easily gobbled up(They are literally fish chow chow right now). My friend got 2 of the small ones too but she can't take more. I only have. 17 gallon tank; 16 gallons of water can be safely kept. There is nothing but a filter inside. I keep an average of 1.5 teaspoons of salt on and do a 60% waterchange every weekend or when needed. I also keep an average of 3 drops of a blue treatment liquid, which i was told was a much lower dose than that used for a 3 day treatment and helps with injuries, parasite problems, bacterial and fungal infections. But this is from a shop that also sold me stones and plastic plants which were possibly causes of problems such as columnaris(a companion fish, 9", i got for her died) and food such as dried shrimo and small red usual fish food which another shop told me was unsuitable and earned me a weird look. I am now feeding the one female i have - freeze dried tubifex worms. She started of in a bucket. Went back there for a while when the columnaris incident happened and now she is back again in a barren tank. She grew an inch from 10" to 11". If she survives, I may volunteer for the other fish. SHOULD I? IF I DO, WHAT DO I NEED TO DO? The filter i was given from the first shop seems pretty okay, though needs to be washed often. They told me it was "double" or something which meant the tank needed to be cleaned once in 4 months (i wonder) in comparison to once in 2 months for the smaller filter they first showed. It is a sponge filter. So: Tank- 22"/16"/11.5" Water- 16 gallon Salt - 1.5 tablespoons, Fish Cure, blue liquid- 3 drops Filter- Sponge, Speed/ Pressure can be changed by opening or closing the cap a bit. Nets- 1 blue 10"/7" for fish and 1 yellow 4"/3" for food issues. Pump- 1 Blue. To take out water from specific areas or in general. I have no kit or further equipment. There was a oxygen thing but it just electrocutes me so I thought it better not to experiement that with the fish. I have no idea what else to do, or not do. Any comments are appreciated. Advice too. pls pls. ps- she kept cutting herself by banging, hitting and basically trying to displace thetop, so in the end i just left it open. how do i manage it so this doesn't have a negative effect on her health?