External canister filter in a 85 gallon tank?

Recently i have been to an aquarist (stores) here in my place {Karimnagar(county), INDIA} to buy a fish bowl for my sister for her birthday, looking at the variety of fish i was very much fascinated to buy a turtle which i have seen there. As i did not wanted to buy a huge tank i asked the guy if turtle is happy in a bowl, and tht rascal said YES. Bought the turtle and was happy, later i felt the turtle wasn't joyous and i started browsing over the yahoo answers and found out everything about the TURTLE TANK, and immediately ordered for a 90 Gallon tank, that hopeless aquarist took a weeks time to get it, i was not able to find a turtle dock and a UVB lamp all over my place and also in the next CITY, so i attached a gl slab at the top and decided to put on some stones for the basking, it took many days for the setup due to the improper resources here, finally the turtle in the tank but with a small filter, between i was searching for an external canister filter, but by the time i bought it, due to improper basking i guess, the baby turtle ped away, i felt really bad, now as its difficult to find all those here i have decided to convert my tank into a fish tank, i have already had algae eaters and shark like fish in it, now i bought a pair of silver dollar, planning to get a pair of blood parrot fish and one single fengshu fish(long white coloured slender one), can you please suggest me whether should i use the external filter (1400L/hr). If i use this external filter how often will i have to change the water? and i want some beautiful colorful fish in my tank, a little expensive would do but not too high though, so could u please suggest me what all fish i can put in the tank? I'm completely new to this, and really fed up with these aquarists here who have almost no knowledge, like for example when i ask for an external canister filter and a UVB lamp they say i'm just wasting money buying all that for a turtle and also say a UV lamp would kill the turtle, and finally ******** killed it, excuse my language, kindly help me maintain my fish tank healthy...!