CORY CATFISH helps???

[OMA]

Is it true that CORY CATFISH is recommended with goldfish as it helps in keeping the tank clean??
i don't know much about this species..
I have a F.W 30x12x12 with 4 Goldfish ( 5inch +) along with a pair of sharks (7 inch +) since 2 years..
i feed them with local food available at LFS (small granules/ balls)
its a bit difficult to maintain the tank as i have to do a 30% WC every week or so
do i need to keep the CORY CATS As well???
will it help if yes wat breed is best suitable for my FW tank??
herz the pic for better idea...
http://www.flickr.com/photos/35414455@N06/3319095101/

[Dragon]

I think Manoj will be able to answer this...

[avadhoots]

1st of all sharks and goldfish are not compatible. Goldfish are cold water slow moving fish and sharks are fast moving tropical fish. Also sharks grow very large.

[Manoj]

Cory cats are scavengers and people keep them in elaborate setups, to finish off the uneaten food that gets into the gravel and decorations, where the carps cant get to it. Yours is a bare bottom tank and carps are greedy hogs. I am sure none of the food is left over by your fish. Beacuse of this, you dont need to keep any cories...

[shubhankar.bivalkar]

To add to avadhoot and Manoj,nothing can substitute a good old water change Trust me no fish,no filter! Your fish will love you for the regular WCs.