Powerhead for clown loach tank.

[Trollboy]

What lph would you recommend for a 200x50x70 tank to give enough flow to keep my 15 loaches happy?

[Diana]

200 x 50 x 70 = 700,000 ml = 700 liters.

I would suggest the total water movement (filters and power heads) about 20 times your tank volume per hour, so 1400 lph.
If this is a hillstream tank then you are probably looking at even more than that.

My set up is something close to 10x the tank volume through the filter, then more with power heads. How much more varies with the set up: Calmer for some fish than others.