one of my brothers tanks has just 1 12" tropical cat fish in it cream and brown colour will the filters donation off just that one be enough to get me going or is off that one fish not enough?
Probably the only ways to know is to test the waters...
1/Test your brothers' water for Ammonia, NitrIte and NitrAte.
2/Transfer sufficient amount of his media (be it sponge, ceramic 'balls' or 'noodles') into your filter, then test that.Your next step will then be to add an ammonia source into your tank and test the water again.
Now would be a good time to do this as you do not currently have any fish, giving you a choice now of 'fish-in' or 'fishless' cycle. As you have read previously, a 'fishless' cycle is always recommended on here.. and with you already having potential access to mature media, you MIGHT already be halfway there !
So, what i would do...
1/Ask your brother for some of his media. When you are sure of what media he uses, how long his tank has been running and a set of his water test results then post it on here, the more experienced members will be happy to advise further.
2/Once the sufficient amount is transferred across,continue a 'fishless' cycle. It may take 2/3 days, it may take a week (mine took 9 days including my 'Qualifying Week' as i had access to mature media like you).
3/Use this time to research into what fish you could possible keep, keeping PH,Temp and compatibility in mind.
But most of all, follow the advice on this forum.. it WILL get you the results and tank you are looking for.
Terry.