im using a uv as of a week ago and would say they are worth every penny they cost..... i had cloudy water for months and turns out it was a algae bloom....... got a uv and 3 days tank is crystal now...... my zapper is a 24watt bulb and does upto 400ltr tank and cost arount the $130 and its just plug and play (no plumming needed)...... well worth the investment