I'm looking to make an external refugium out of a 10 gal. tank and LS and LR from my main tank. What kind of filtration(would a powerhead alone be enough)is needed and what kind of lighting.???
A general rule for flow is 3x-5x the refugium volume. You don't really need any additional filtration since you're just pushiing tank water though it. Let your main tank do the filtration. If you just want to grow marcoalgaes and 'pods in the refugium, an aquarium plant grow light will do fine; no need for expensive MH or VHO lighting, but if you're going to keep a coral or two in it then you'll need what ever lighting they require.