Fish totals in Freshwater tanks

Question
I have anew 29 gallon freshwater tank.  It is approx. 12" x 30" by 19" high.   I have read all of the methods to calculate the total number of tropical fish you can put into this tank.  My question is "Do catfish & bottom feeders count against this total?  I am told I need 4 - 5 catfish to properly maintain the tank.   Will these count against the total number of fish, or since the catfish are elinminating waste in the tank, do they cancel themselves out of the equation?

Thanks

Answer
Hi Phil,
The method to calculate how many fish can be in a tank is sometimes inaccurate beause obviously you cant have a 10inch fish in a 10 gallon tank.  But it is still a somewhat good way for a general idea.  To answer your question, it counts if they are big, and will cancel themselves out if they are small.  If the catfish you are getting do not get big, such as cory cats, or otocinclus catfish etc then you will definitly be ok.  There are some catfish that get big.  For your 29g, I would suggest any catfish that doesnt exceed 6 inches max.  Just research the species before buying to make sure.
-Matt-