Mr. Saltwater Tank

Write-Up Wednesday: 3 Phosphate Removing Medias and My Experiences With Each

Phosphate (PO4) is directly related to algae outbreaks and coral health as lower phosphates (<0.03 ppm) usually mean less algae outbreaks and healthier corals. I say “usually” because every tank is different. Some tanks do well on lower phosphates, some do not (Hint…Chemistry and Tank Automation Program participants…this is right up your alley.)

On all my tanks and on my client builds, I always have at least one method of phosphate control running at all time with the most common method being phosphate removing media placed in a reactor.

I’ve used lots of phosphate removing medias and these are my experience with the three most common ones: RowaPhos, PhosGuard and Granulated Ferric Oxide (GFO).


RowPhos or “rowa” for short is widely used in Europe. Availability in the USA is somewhat limited as I don’t see it in local fish stores as much as the other two products I’ll cover. RowaPhos is a small sized media that comes in a bag. That bag is placed in your tank or sump. Any attempt I’ve tried to remove the media from the bag and place it in a reactor hasn’t worked as the particle size of RowaPhos is small which means the media blows out of the reactor. Just placing the bag of RowaPhos in the reactor is very inefficient as most of the water flowing through the media bypasses the bag and little or no phosphates are absorbed. Because of the higher cost due to import duties, the inability for me to buy it in bulk, and since it doesn’t work well in a reactor, I don’t use RowaPhos in my tanks.


PhosGuard is an aluminum oxide product made by SeaChem. The media looks like small white balls and the balls are large enough to be placed in a media reactor and not get blown out of the media reactor. PhosGuard is available in bulk which is great for large tank guys like myself.

Hobbyists will often get up in arms about PhosGuard as it is an aluminum based product and is rumored to leach aluminum into your tank water. Aluminum is also thought be harmful to corals hence the concern for those of us with reef tanks. SeaChem released a research paper on the solubility of aluminum oxide and concluded that “The results of these experiments show that under reef conditions (pH near 8) there is no detectable soluble aluminum released from alumina. Under conditions of low pH and high dosage levels, soluble aluminum can be released from alumina; at three times the label dosage rate, we detected 0.2 mg/L aluminum at a pH of 5.3.” (full paper here)

Here’s a hint…if the pH gets to 5.3 in your reef tank, your coral and your fish, will be long since dead.

I personally don’t use PhosGuard in my tank as Granulated Ferric Oxide (GFO) absorbs much more phosphate. If you can’t get your hands on GFO, then PhosGuard is a good alternative.

Granulated Ferric Oxide (GFO)

GFO is an granular iron based product and is widely used for phosphate control due to it’s low price, widespread availability and high absorption capabilities. It comes in several grades and my experience has been that the “regular” grade works fine. Therefore, I don’t recommend the higher capacity GFO products.

GFO doesn’t come without drawbacks though. It can easily clump up in a media reactor and must be thoroughly rinsed before being placed in your systems.

Since I can easily buy it in bulk at an affordable price and I’m ok with the added maintenance of GFO, I use regular grade GFO on my tanks.

Phosphates are a parameter I monitor in my tanks and phosphate absorbing medias are the easiest way I’ve found to keep my phosphates in check.

Browse the Store! Questions?

Comments for this article (23)

  • Allen says:

    What do you think about chemi-pure and purigen?

    Also I’d like to hear your thoughts (if you have already done it) on different brands of GAC.

  • Joel says:

    All my local stores are pushing the chemi-pure now. Have you had any experience with that product?

  • Dennis says:

    What brand and size reactor would you suggest for a 55 gallon tank ? I’m currently having an algea outbreak (green and red cyano) and this article has me wanting to get a reactor…

  • Richard says:

    What’s your thoughts on lanthanum chloride?

  • David says:

    Mark, or anyone else, have you tried the Brightwell Aquatics Xport-PO4? It looks like giant lava/grill rocks!

  • Marc Scavuzzo says:

    I wanted your take on Red Sea No3 Po4X to reduce Phosphates as well as Nitrates. With the carbon dosing, my Phosphates have come down to acceptible levels but the Nitrates are still high.

  • Dave says:

    I was surprised you didn’t mention lanthanum at all for phosphate removal. Used only in extreme situations (aka at wit’s end) many people swear tthey have achieved great effects from using this method.

    Also, although I personally have no use for biopellets, I think it would be worth noting that a system needs to have some phosphate present for biopellets to be effective at controlling nitrates. If a system is using both biopellets and GFO at the same time it seems to me the user is working at cross purposes. Do you disagree or have any further comments?


  • Jason says:

    Since when is GFO cheap? Not sure if I am missing out on something, but I usually use BRS GFO and it’s far from cheap, imo…lol.

  • Ondrej says:

    Hi Mark,
    I do t know what rowa you get in states but I have not seen it in bags in the uk. We get it in a form similar to BRS gfo. It’s small, get everywhere and expensive.
    I have had a great result with fauna marine ultraphos- you can get it in aluminium or gfo version.
    Also lanthanum is great. To bring things to manageable levels (tangs don’t like it as it effects they gills and can kill them )

  • SantaMonica says:

    I am of course partial to natural P removal via algae, especially when the photosynthesis of the algae is increased by a scrubber. Scrubbers cannot “over scrub”, because they use the same mechanism for filtering (photosynthesis) that corals use to grow. So, when nutrients are low, both react the same. The opposite can be said of pellets, gfo, nitrate reactors, etc; they don’t care what the status of the corals’ photosynthesis needs are.

  • Randy says:

    Joel…Chemi-Pure is ok but for me it doesn’t last as long as GFO. I go months without changing GFO and my phos reads 0 or little to none. Can’t beat it.

  • John says:

    Mark, I also would like to know where You get bulk gfo at a affordable price. Its just rust and is very expensive at brs i think. I still buy it but and use it 24/7 but it hurts the wallet !

  • Nick says:

    SantaMonica: The main problrm with algae scrubbers, or refugiums, is that whilst they can not over scrub, they can very easily under scrub. They can also remove to much iron. iodine, and potassium. If you follow manufactures guide lines with gfo, then it is very difficult to suck your tank 4 below 0.005 po4 of natural sea water.

    Mark You can use Rowa just like any other gfo. Just let it tumble Gently, or mix with activated carbon, and place in reactor between filter sponges, so it does not tumble.

  • Eddie Wong says:

    Mark, I use Rowa concurrently but I do not know what is the “GFO” do you have a picture. Thks

  • Vasco Jardim says:

    Hi Mark, i also use Rowaphos (Europe) and it comes in bulk, not in a bag. I believe only the small package comes in a bag. Rows is indeed designed to be used in a media reactor and Deltec makes one (I believe it is the FR509) that is widely used as a Rowa reactor.

    The reason I stopped using it and went with Phosguard is because Rowa makes a huge mess and has a tendency to clump. I love Phosguard’s spherical shape that allows for perfect water water thrue and never had it clump.

  • Dave says:

    I’ve been using NO3/Po4-X by Red Sea and have gotten excellent results. My Nitrates are undetectable and it took a while buy my phosphates have dropped to 0. I’m really happy with the results I’ve been getting and run PhosGuard or PhosBan in my reactor only as a backup. My phosphates without these two products has still kept my phosphates extremely low to 0. I test with Hanna Instruments ULR Phosphorous test to get a better picture of my total available phosphorous.

  • Eddie Wong says:

    Can I make it clear ROwa & GFO is it same materials with different name/brand. Thks

  • John…I buy it from BRS.

  • John says:

    Why not just use a Kalk reactor? It binds to phosphate and renders it chemically inert. Plus, it adds calcium, keeps ph high and it’s cheap. Simple is sometimes better. Just my 2 cents.

  • John..kalk doesn’t bind a lot of phosphate especially when compared with these media. Also, you can over dose kalk quite easily especially if your tank isn’ deficient in calcium or alkalinity.

  • donny whalen says:

    hi Mark.
    i wonder why you never mentioned dr. tim’s pearls, i have been using them now for a while, just ordered more actually, and i have had excellent results with both phosphates and nitrates at zero or close to it. its only since they’ve depleted some that my levels started to rise a small bit. I’m running a 220 gal 40 gal sump mixed reef tank about 250 lbs live rock and my clean up grew numbers are lower than recommended. just wondering your take on it.

  • Dave (UK) says:

    Hi Mark,
    I use RowaPhos in a small reactor in my sump, It does work well. As long as you position the disc shaped sponge provided at the top of the reactor, there is no leakage of granules back into the sump.
    Also, adjusting the flow so that the granules simmer like garden peas in a hot saucepan on the hob will keep the media absorbing without escaping and prevents it from clogging up into a solid lump.
    Prior to using it in a reactor I did just place it in a bag in the sump and it wasn’t effective and clumped up into a solid mass. Internet research highlighted that a reactor was the only effective method of using RowaPhos; otherwise save your money!

  • Joe says:

    I use RowaPhos and Chemipure Elite in a dual chamber reactor (BRS), for nearly a year now with excellent results and long life, with a low tumble. 225g display, mixed reef. I’ve tried many other products with limited results.

Comments are closed.