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phosguard in place of DI resin?

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  • phosguard in place of DI resin?

    So I have a small high tech planted tank, my tap water is highly carbonated which depletes the DI resin in my RO unit in about 15 gallons. So I am unable to use DI resin while living at this location.

    I don't really care if I have like 5 tds water source but I think silicates are slipping through.

    I want to know if it's safe to fill my di resin canister with phosguard, or if it will leach something into the water when used in bulk as a pre-filter.

    It's a 10 gallon with EI dosing, co2 and a nice led light for planted tanks. Light isn't even on all the way. It has a air stone and a hob filter. Substrate is flourite brown, I rinsed it probably more than anyone ever has. Not sure if that product contains silicates, if so then my substrate isn't helping.

    I add phosphates in the EI dosing due to the plants needs. I'll probably do some phosguard during the night every other night then yank it out before dosing the fert rotation with phosphates for the day cycle.

  • #2
    Thanks for the post, Ben3721!

    My only concern would be that a single pass through the media may not remove all the silicates. Typically, PhosGuard goes into a filter where the water is constantly passing through it, which then removes any phosphates/silicates. Have you tested your actual silicate level in the water? If so, what is it?


    • #3
      I have not bought a test kit for silicates, honestly didn't know a freshwater test kit for silicates even existed. I've never had luck with some of the test kits, they go bad very fast or before I even get them. Namely the api gh, kh, and phosphate test kit rapidly go bad.

      I ordered the seachem silicate test kit and more phosguard. Currently I'm leaving in the phosguard during the night in my tank, thats saved me in the past, just looking for a long term solution. I do the 50% wc every week then an extra if my tds spikes too high.

      I'll test my ro water to see if it has any. I'll have the test tomorrow thanks to Amazon 1 day shipping.

      Edit: This guy apparently with the exact issue did exactly what I did. But I have no idea how well it worked for him long term.
      Last edited by Ben3721; 09-07-2021, 17:28.


      • #4
        So I ran the silicate test, good news and bad news. It appears my ro water is totally fine. Test is almost clear. It doesn't match anything on the test sheet. But the water from the tank is closer to 4. I assume that ppm so that means my silicates are way too high.

        Thing is, other than seachem equilibrium, and EI dosing nothing else goes into the tank. So I have to assume the seachem flourite brown is leaching at least 1ppm silicates per week into the water somehow. I recently did some planting that may have kicked up more dust than normal.

        So now what do I do? I can't run a phosphate/silicate remover 24/7 for years without causing a phosphate deficiency in the plants and green spot algae.

        I could try switching from the seachem flourite brown to something else, but id rather not gut my tank for the 3rd time this year.


        • #5
          Thanks for the update!

          All of the Seachem gravels are inert and do not leach anything into the water column, so the Silicates should not be coming from the Flourite. Do you have anything else in your tank besides the Flourite gravel, i.e. decorations? You could certainly try the setup that you researched and see how well it works for you. The main goal in a planted tank is to maintain a level of nitrogen and phosphorous for the plants. Typically, if you can aim for about a 10:1 nitrate:phosphate level, you should not have any algae issues and your plants will remain happy. You just don't want to strip all of the nitrogen and phosphorous out of the tank. With that being said, if you have a lot of fish and inverts in the system, they will also help to produce those nutrients via their waste and uneaten food you give them. Sometimes, hobbyist don't even have to supplement nitrogen and phosphorous because they get plenty from the inhabitants to keep the plants happy and the algae in check.

          If using the PhosGuard in the filter, you will just need to keep a close eye on your levels to ensure they don't go to zero.


          • #6
            So now it's sitting about at 1.3mg/l

            The tank has driftwood, the co2 diffuser and a air stone. I will swap the air stone to something else and see if it helps, it's one of those glued sand ones.

            If silicates still come from no where then the only possibility is the substrate. When I got the substrate it was muddy and wet in the bag, which is unlike the traditional flourite (redish but not labeled as red) I had from years ago.
            I may take some of this new flourite brown and shake it in a tear tube then drain only the water out and run a silicate test on it, or let it sit for a few days before testing.

            I understand what your products state and that you guys stand behind it, but I need to know what's going on.

            Edit: the air stone has been replaced with a plastic one which works fine.
            Last edited by Ben3721; 09-22-2021, 22:27.


            • #7
              Thanks for the update! You could take a cup or two of the Flourite and place it in a small container with RO water and let it sit overnight. I would recommend testing the water before placing the Flourite in it and then after the Flourite has been sitting in it for 24 hours. This should be a good test to see if it is leaching anything into the water.