GFO Phosphate Remover, Granular Ferric Oxide, for Saltwater Aquariums (20lbs)

I prefer to not use socks because of the amphipods and copepods in my large mixed reef saltwater system, which is probably why a pound of this powdered GFO lasts me almost 3 years. I'm back for more, but like everything else in the aquarium hobby the price has gone up since I first got this. However, this powdered GFO is still among the most affordable options for reducing phosphates. They say 'rinse, rinse, rinse' but I'm lazy. Because I'm using a bag to hold my GFO plus filter sock to hold the GFO bag, I let the filter sock 'rinse' but I enclose a photo as some of you may not like that super fine powder that escapes the bag to be running around in the sock... but I figure even that fine powder is reducing phosphates so I'm not wasting the extra fine powder most probably rinse away and I find it is kept contained by the sock. Also, to the guy who complained about his fine bag - compare his photo of bag to my photo of bag. A fine mesh bag designed to hold powdered filter media is going to appear like solid thin fabric so that other guy was doomed just by his choice of bag. Don't just go with any bag that says it is fine - actually LOOK at the bag to ensure it looks like what you need for fine granules. You'll find many more uses for this grade of mesh, so that is what I keep around for my various aquariums needs.I have media reactor that I use cubes coated with GFO but that is a more expensive option than this powdered GFO. When the cubes exhaust their phosphate absorption and/or my reactor gets gunky, I usually am living life too busy and I have a mess on my hands I have to get under control asap so death doesn't keep rolling through my corals from too high phosphates. I like this option because it is easy and results are immediate. I use a very fine mesh bag and I just pour in this GFO. Then I put the mesh bag filled with GFO into one of my two filter socks (dual overflow system) that are in the first chamber of my sump. This forces more water thru the GFO in the fine mesh bag than if the fine mesh bag were just laying on the bottom of my sump or even if I tried stuffing the bag between sump section baffles, as water wants to take the path of least resistance which is going around my fine mesh bag stuffed with GFO. When my socks get dirty, I throw those in a bucket and collect a bunch before I deal with the sump dirty socks. I put new socks in place and just move the GFO from the dirty to clean sock, as the GFO is still in its fine mesh bag I tied shut. If you use socks or if you have a media reactor designed for powders, this powdered GFO is absolutely the easiest and most affordable way to reduce phosphates.

Really dusty and extra small grain sizes. Make sure you have a really fine mesh bag or reactor. Works quickly.

As several others have noted, the granularity is very fine, and there is a fair amount of product dust. This really needs to be used with a media reactor, not just a filter bag. The larger the reactor, the better, so as to let smaller particles fall back down.That being said, this product is at an excellent price, and controls my phosphates well in my 300g mixed reef. When phosphates start to climb, for the first time, I just top off what is already there with another 1/2 - 1 cup. This gives me a little more time out of the product as a whole, rather than just throwing the entire contents out.This is my second purchase of this product, and everything has been consistent.Hope this review helps others.

This GFO has very small granules. i needed to sift it to get all the fine particles and dust out. I have a DIY reactor with a fine mesh screen and this GFO clogs the screen very quickly, even after sifting and rinsing. Maybe i will need to get a different reactor, but It seems like this is a common issue with this GFO.

I try to buy bulk consumables as much as possible. For the time being I fill mesh zipper bags with the GFO media and put them inside my hang on back filter. Soon I will be switching to a more efficient way to use the media. I purchased a universal media reactor for different types of media. I plan on mixing GFO and Activated Carbon and filling the reactor with the mixture. By using a DC pump I can control the water flow through the reactor for best results.

I'm not sure what all these other reviews are talking about with the high dust. I rinsed mine pretty well and it did have a little more dust once turned on, but my tank cleared up. I have the reactor infront of the skimmer so that it catches any by product released from the reactor. All depends on your filtration if you ask me. NOW, this product works! My phosphates were at .16 ppm and this GFO reduced them to .04 ppm after one day! This product works. Just know how to use it. Rinse it, rinse it again, and rinse some more. Then add to the media reactor, you don't need much. If you jam pack the reactor then it will clump and sludge. I didn't even use the recommended amount from the bad directions, I used less and it still worked! You want the media to gently tumble in the reactor and not going too crazy. If you know how to use it, then it will yield great results.

I added it to my filter and saw results within 24 hours. After a few days my phosphorus was almost undetectable. I tried many other products, but this one worked great. And it didn't affect any of the fish or seahorses in the tank.

I have been running reef tanks for over 20 years. This is hands down the worst product I have ever bought. I literally spent over 50 gallons of RODI water rinsing the dust from 4 pounds of this trash and it’s STILL filthy. I have a 750 gallon system and after 5 minutes of running this through my reactor I can’t see 3” into my tank. Do not, I repeat, DO NOT waste your money on this inferior product. I have never, in all my years of reef keeping had a product fail so badly. Please learn from my mistake and avoid this product like the plague.