A tenant who recently moved out left behind a fish tank with six fish in it. It is a small tank - I think it must be about 30 litres. There was no heating or filtration but there was an air stone. After a bit of research I think there are 3 cherry barbs and 3 plecos. I have taken responsibility for the tank and added a filter and heater, but I am concerned about the plecos as it would seem that these are going to grow very large and I am amazed that someone has put three together. They are currently about 3-4". This has prompted me to rekindle an old interest in tropical fish and I am currently cycling a new 125 litre tank, which is about as big as I have room for. Will this be big enough for the current fish and allow me to add others or should I try to find some other way of dealing with these plecos?