Santa Monica Filtration recently released an updated version of its original waterfall algae scrubber, dubbed the RAIN2. When ordering the RAIN2, which retails for $349.99 USD, you can choose 1, 2 or 4 of the GEM5 lights, which will be already mounted to the inside of the dome lid cover. The underwater submersible GEM5 lights allow the RAIN2 to be placed in your sump anywhere you like, as low to the water as you like, which saves a lot of space. And the pole mounting option means you don’t even need a shelf or a bracket to place the unit; just use your pole mount to set it on the bottom of your sump.

Also included is a 2 mm thick, 2 sided, patent pending Green Grabber® algae attachment screen; it’s the modern replacement for the old hand-scrapped plastic screens. The screen is surrounded by air, so that when algae growth is strong on the screen the algae can get the carbon it needs from the CO2 in the air (instead of from the alkalinity in your water) after the CO2 in your water is used up. Thus the scrubber growth (filtering) is not limited by your alkalinity and CO2 in your water, and your alkalinity will stay at higher levels.
The RAIN2 requires a water pump that can pump at least 200 gph (760 lph) water flow 24 hours a day. The height (“head”) of the filter above the sump water level will require that the pump be able to pump up to that level and still be able to supply enough water. The water can also be fed from your display overflow; any type of overflow system (Herbie, siphon, etc) will work.

Here are the differences in the RAIN2 units available:

Aquarium size: The RAIN2 with 1 GEM5 light has 24 square inches of 1-sided growth surface and is designed to be the only filter on an aquarium that is fed up to:

1 frozen cube per day, or
10 pinches of flake food per day, or
10 square inches (60 sq cm) of nori seaweed per day, or
0.1 dry ounce (2.8 grams) of pellet food per day.

Each 50 pounds (23 kg) of phosphate-soaked nuisance algae problem rock counts for an additional 1 cube a day. The level of light of the 1 GEM5 light works well in saltwater when nutrients in the water are low. Up to 3 more GEM5 lights can be added at any time with silicone glue.

The RAIN2 with 2 GEM5 lights has 24 square inches of 2-sided growth surface and is designed to be the only filter on an aquarium that is fed up to:

2 frozen cubes per day, or
20 pinches of flake food per day, or
20 square inches (120 sq cm) of nori seaweed per day, or
0.2 dry ounce (5.6 grams) of pellet food per day.

Each 50 pounds (23 kg) of phosphate-soaked nuisance algae problem rock counts for an additional 1 cube a day. This medium level of light of 2 GEM5 lights works well when nutrients in saltwater are measurable. Having lights on both sides of the screen allow it to grow a few more days before the growth starts shading the algae roots. Up to two more GEM5 lights can be added at any time with silicone glue.

The RAIN2 with 4 GEM5 lights has the same growth surface area and feeding as with 2 GEM5 lights, but the high level of light of 4 GEM5 lights works well when nutrients in the saltwater are high.

For more information, visit the Santa Monica Filtration website.