Anywhere in the blue range works fine. These are a purple color and aren't as dazzling to the eye but does a fine job of nuking about anything you hit it with. Distance, focus, tank clarity all contribute to how effective it is. It takes more power if you use a green laser because of the absorption colors underwater organics are.
The 405nm laser led
concentrates a very small dot so it's energy density is higher than some others. In a perfect world you would use a C02 UV
laser at about 20 watts with a visible guide laser, but that's out of most hobbyists rang, thank heavens.
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