Santa Monica Filtration

HOG2x Freshwater Hang-On-Glass Upflow Algae Scrubber - Santa Monica Filtration


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The world`s waters, from the sea to the mountains, are naturally filtered by algae only to leave any other organic particles to float freely and feed aquatic creatures. Algae is an excellent environment for for many microorganisms to live, of which can be swept away into the water column to become part of the natural food chain.

The patented designed HOG2x is a hang on glass, upflow style, algae scrubber harnesses the ability of algae.  Algae Scrubbers help reduce or in some cases eliminate the need for waterchanges, also aiding in removal of nuisance algae, nitrate and phosphate.  Algae scrubbers can also provide nutritious algae for certain fish and invertebrates when cultivated.

The HOG2x was designed for freshwater use, with a stronger light for nitrate over 50 ppm, and easily fits on aquariums 1/4" (6mm) to 5/8" (16mm) thick (acrylic or glass).

Get the no-overflow advantage of an upflow scrubber: since it is ALL underwater, it can`t overflow onto your floor. Just nice soothing bubbling like you probably already have in your freshwater tank. And since there are no strings (like our HOG3), it`s easier to brush the freshwater growth clean in your sink.

This HOG2x scrubber has 48 square inches (300 square cm) of one-sided freshwater algal growth surface, which once growing is designed to absorb the nutrients from this much feeding per day:

  • 2 Frozen cubes, or
  • 20 Pinches of flake, or
  • 20 Square inches (125 square cm) of nori, or
  • 5.6 grams of pellets

The number of gallons or liters of water in your tank or sump does not matter. If you feed more than the above amounts you can get multiple HOG2x units; multiple units are preferred over one larger unit because you can clean one unit per week, and because you`ll always have one unit filtering while the other one starts growing again after a cleaning. Multiple units are also good for backup.

The magnets attach the outside cover to the inside cover through the aquarium or sump glass, and can be used on glass or acrylic 1/4 inch (6 mm) to 5/8 inch (16 mm). Not more. If your aquarium wall is 3/4" (18mm) it might work but you won`t know until you try; it would be better to put the HOG2x in your sump instead; it will work the same.

Click here for more images of the HOG in action: Santa Monica Gallery

Compared to the HOG2 which looks the same, the HOG2x has Xtra light and is meant for freshwater tanks with nitrate over 50 ppm. It will still work with saltwater, but the thicker growth you get in saltwater is better with the strings on the HOG3. The HOG2x has the exact same 6 LED lamps as the HOG3, but with the freshwater Green Grabber growth surface of the HOG2. So this HOG2x is optimized for freshwater growth conditions.

The Green-Grabber® algal growth surface is so rough and prickly that it might be the roughest thing you`ve ever felt. A cactus might be sharper, but that`s about it. Rough surfaces are critical for allowing algae to attach and grow and thus provide strong absorption of nutrients. The rock-hard protrusions stick straight out 1 to 3 mm. Old style algae scrubber screens are made from "slippery" plastic canvas that is used for sewing and knitting; algae takes a long time to attach to it. Green-Grabber® growth surfaces are not plastic at all; instead they are rock hard and have jagged rough edges and points (don`t let children play with them). And the white color of the Green-Grabber surface reflects as much light as possible, getting almost the effectiveness of a 2-sided growth surface even though it really only has a light on one side of the surface.

This is a hand-built Hang-On-Glass® (HOG) Upflow Algae Scrubber® (UAS) with a Green-Grabber growth surface, for glass or acrylic 1/4 inch (6 mm) to 5/8 inch (16 mm) thick. This is the typical thickness range for most aquariums, and larger sumps, however you should measure yours to be sure. If your tank uses thin 1/8" (3mm) glass such as many low-cost 10 gallon aquariums do, this filter is not recommended because the magnets are strong enough that they might crack the glass. 

No electrical parts go inside the aquarium; only air. And the air bubbler is already supplied (it`s sealed behind the growth surface), so you don`t have to get an airstone. The bubbler is simply vinyl air hose that has been cut lengthwise, and with cross-cuts, to form little flexible segments that are both adjustable and open-able to allow for easy cleaning. This HOG2 will run on both 120V and 240V, and comes with a 10 ft (300 cm) power cord with a U.S. plug. If you require a different plug you can get an adapter at any local hardware or travel store, or online, or you can cut off the U.S. plug and install your own plug from a hardware store.

Comes with 3 ft (90 cm) of vinyl airline, but requires an air pump that can pump at least 2.0 liters per minute (.07 cfm), preferably more. A pump that says it can handle 2 or more airstones/outlets, or a pump with 2 tubing attachments instead of one, will be needed. You can have as much air as you like, however; 10 lpm pumps are no problem (although it will be louder). One powerful pump which works exceptionally well for a low cost is the Fusion 700 Air Pump from JW Pet. It is quiet and has two outputs which are adjustable by turning the control knob. Another even more powerful and completely silent pump, although more expensive and without a control, is the Whisper AP 300 from Tetra. With either pump you will need to combine the two outputs into one to feed the scrubber, using something such as the "Tee" air line tubing fitting from Tom Aquatics (which we include with the Fusion 700). Make sure to put the air pump above the aquarium so that it will not drain any water if it shuts off.

Comes with 6 red (660 nm) 3-watt LED lamps, which are attached to a heat sink inside the cover. The LEDs will give the aquarium or sump a slight red color at night when the aquarium lights are off. You might need to get a timer so you can run the LEDs for less than 22 hours per day, but you can try 24 hours (no timer) first and see how it goes. The LEDs never needs replacing.


  • Dimensions per cover: 6-5/8" L x 1-1/2" W x 8-3/4" H  (16.6cm wide x 3.75cm thick x 21.9cm high)
  • Operates on both 120 and 240V
  • No dangerous metal 240/120 volt lights

Use Guidelines / Tips:

  • The growth surface will need to be cleaned every 5 to 14 days, by removing the inside cover, disconnecting the airline, and taking the inside cover to the sink so you can brush the algae off of the growth surface and the bubbler with a toothbrush.
  • No hard scraping is needed; just brush it with a toothbrush or larger brush.
  • The Green-Grabber growth surface is permanently glued to the inside cover using epoxy, however a few of the Green-Grabber particles may dislodge during the first few cleanings, which is normal.
  • Cleaning the growth surface, bubbler, and the inside cover takes about a minute with a toothbrush once you are at your sink.

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Takes a while to start growing
Helps keep water numbers in check which makes for fewer water changes
I wish it was a way to turn off half the led lights during the initial algae growth period but the black clothe is the low tech solution.
Took me about 2 months, but a lot of adjusting and then waiting, but this was in a 90gal new tank that hadn't cycled yet. Water reading are right on point in my freshwater community tank (Tetra's, Danio's, Angel fish ect..28 fish). It works well in tank with live plants, and it looks like fewer wate...Read More
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