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  • non-CO2 filtering

    I've decided to convert my main tank (50G) to non-CO2 for now, because I want my tank to be more maintenance free -- I've been spending a lot of time traveling (by my standards), and I think this is my best option (at this time).

    I've read up on the non-CO2 method (Tom's version) and understand the basics. Luckily, most of my plants should do fine in a non-CO2 environment, so I will not have to do much re-scaping. I put together a 10G non-CO2 tank a number of months ago, and it has been doing quite well. However, the one thing I'm not sure about is filtering, so here are some questions:

    1) Should we still go for a high flow rate on a non-CO2 tank? I was thinking to go about 400 gph.

    2) Do we still filter the water very well? It seems that a non-CO2 is more of a self-contained eco-system. I was wondering if perhaps it's a good idea to filter less so detritus (decaying leaves, e.g.) can dissolve and be re-used by the system. I've actually been working on a DIY sump and have some very fine filter socks I was planning to use. I'm not even sure that I should use these on a non-CO2 tank (maybe a sump isn't even a good idea).

    Thanks in advance.
    Last edited by tedr108; 08-11-2008, 01:05 AM.

  • #2
    1. Circulation on a non-co2 tank especially is extremely important. This is now the only way your plants get co2, without that circulation your plants get extremely co2 starved.

    2. I think there are many schools of thought on this one. What you are suggesting is a little more towards the 'el natural' tank method (low/no filtration, few water changes, a sort of enclosed ecosystem). Personally, I've tried both the strict 'el natural' method, as well as regular non-co2 and co2 tanks dosing EI. The easiest method (maintenance wise) for me has been the regular non-co2 method with maybe sort of 'relaxed' EI. The few water changes/low filtering method bombed for me with major BGA issues as well as pretty much every other algae under the sun. It got so that I was spending more time removing bga than I would have been doing water changes and fertilizing, and my plants were gradually dying or getting overtaken by algae. I believe this method can only work consistently with an extremely light fish load.

    My easiest tank is my 10g non-co2 tank. Plant growth is slow, but steady (pruning maybe every month or six weeks or so), I have few algae issues, and I only do water changes about every 2 weeks or so and if I miss a week, the system doesn't crash. I dose approximately 1/4 - 1/2 EI dosing once weekly of all micros/macros and only change about 30 - 40% of the water each water change bimonthly but I do a very good gravel vac. This seems to keep things stable enough for plant growth, as well as removing excess organics from building up in the tank that contribute to algae and the plants are very happy. I just have a regular hob on the tank (which I rarely clean) and an airstone. The additional circulation really perked up the whole tank when I added the airstone. Low light is also a plus.

    So I don't think that leaving excessive waste in the tank to decay will contribute to a healthier tank, I have found it better to still dose fertilizers at leaner rates while keeping up with a certain amount of cleaning of the tank.

    If you are switching from co2 to non-co2, you may find it helpful to reduce your lighting for a while and do more frequent water changes until the plants readapt. The reason for this is that when co2 is cut off, algae will begin to take hold in the time period between when you stop co2 and when your plants readapt to lower co2 rates. This adaptation can take up to a month so during that time you want to make sure that you do everything you can to reduce the propensity for algae.
    Last edited by Carissa; 08-11-2008, 08:03 PM.
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    • #3
      Thanks for the informative post, Carissa.

      I think I'll go with the regular non-CO2 with "relaxed" EI. I have been doing that in my 10G non-CO2 for about 6 months, and it is doing well. I like the idea of keeping my water clean. And, if I can keep a few more fish that way, all the better. Maybe I'll get another 10G and try the "el natural" method in the future.

      You saved me from having a big algae mess, I'm sure, because I was not planning on a slow transition to the non-CO2 method. I am glad that you mentioned this. I've been letting my 10G non-CO2 get overgrown on purpose -- that will give me a source of non-CO2-ready plants for my big tank, which will help in the transition.
      Last edited by tedr108; 08-11-2008, 10:31 PM.


      • #4
        Originally posted by Carissa View Post

        Personally, I've tried both the strict 'el natural' method, as well as regular non-co2 and co2 tanks dosing EI. The easiest method (maintenance wise) for me has been the regular non-co2 method with maybe sort of 'relaxed' EI. The few water changes/low filtering method bombed for me with major BGA issues as well as pretty much every other algae under the sun.
        Thanks for sharing your experience, but can you elaborate on which method's you are referring to?

        'el natural' would be Walstad, but what is meant by "regular" non-co2 method? The method outlined on this site specifies infrequent water changes, so what you are suggesting would be something different right? Since we are on Tom's site I thought "regular" method would refer to Tom's method.

        Thanks for any help as it would be nice to hear how someone managed a low light non-co2 tank, but with frequent water changes to support a higher bio-load. The method described here suggests that that's a recipe for disaster.


        • #5

          I do not know the Walstad method ("el natural") at all, but I think the main point with Tom's method is that you still have good filtering and clean up the tank (removing dead and dying leaves, etc) when needed. I've been going non-CO2 for over a month now -- haven't changed the water at all and have only the tiniest amount of thread algae occasionally, no other algae whatsoever. Tank inhabitants are 19 galaxy rasboras and several cherry and tiger shrimp ... all are doing great. The way my galaxies and shrimp enjoy playing around, I can tell that the environment is very healthy.

          My main plants are corkscrew vals, anacharis, anubias nanas, red tiger lily (I believe) and java fern. I have a few other plants that are surviving and algae free, but I'm not sure they are going to do much in a non-CO2 tank. I clean my filters and pre-filters (over the filter intakes) often, and prune and clean the tank as necessary. For fertilizing, I add small amounts of KNO3 (potassium nitrate), KH2PO4 (mono potassium phosphate), Seachem Equilibrium and Tropica Plant Nutrition -- using Tom's dosing guidelines for the most part. My nitrates will actually go down to zero or close to it, if I do not keep up with the dosing. I knew my tank plants/ecosystem had kicked in completely when the nitrates finally got down close to zero.

          My water is crystal clear. Overall, this is a great method for my tastes and available time. I do not miss the water changes and constant pruning (my EI tank plants were growing 1" to 2" per day and I could not keep up with it).

          Hope this helps some...
          Last edited by tedr108; 10-02-2008, 07:17 PM.


          • #6
            The Walstad method features a soil substrate and few water changes. Excessive surface movement is not recommended because it would drive off scarce CO2.

            (Now before another debate starts, note that the soil substrate in a Walstad tank generates CO2, and the CO2 level in such a tank is higher than that of the atmosphere in the vicinity of the tank.)

            Ms. Walstad is also not a strong believer in filtration and water movement. Possibly it isn't needed because nutrients are being generated from all over the tank and don't have to be dispersed from the point where they are added.



            • #7
              Thought I would post a pic of one of my non-CO2 tanks (the other was just planted yesterday):

              The above tank was pruned heavily yesterday, so it may seem a little bare -- but, even these non-CO2 tanks get overgrown, just not in 3 days like an EI tank!

              Also, I remember a thread a while back where someone was wanting to know about red plants that would do well in a non-CO2 environment. Here is a red tiger lily (correct me if I'm wrong, please) that someone gave me from an offshoot of theirs a couple of weeks ago. It has already grown 3 new leaves -- not bad in a non-CO2, if you ask me. The pic really doesn't do it justice -- it is more vibrant than it looks here. Anyway, here it is:

              Thanks for explaining the Walstad method, Bill ... I may give it a try someday. It seems a little more work to set up, but it sounds interesting.
              Last edited by tedr108; 10-03-2008, 02:41 AM.


              • #8
                Thanks for your thoughts. The tanks look very nice.

                I'm still not sure what method you are following though? You had said the regular method and since we are on Tom's site I thought you meant his non-co2 method, but his doesn't account for frequent water changes, that's what I'm curious about.

                I found this non-co2 tank:

                330 Liter - "Lower Maintenance Expenses (LME)" Photo Gallery by Oliver Knott the aqua creator at

                and I see that he does weekly water changes, but most info I'm reading here and elsewhere implies that frequent water changes with low tech method's spells disaster. I'm wanting to carry a heavier bio-load so I need to do frequent water changes, but I also want to stay low-tech, everything I read points out that those goals are at odds, yet I seem to see many examples of people like yourself having success this way.


                • #9
                  For me, aquatic plants are a means to a healthy tank and happy fish. I am not much of an artist!

                  The "regular" non-CO2 method denotes Tom's guidelines in my mind...

                  I think you will have to do water changes if you have a heavy bio-load. Actually, I'm not sure what a heavy bio-load would be -- maybe someone else can pipe in here. I do not think that 19 (20 now, since I just returned a fry to the tank) galaxy rasboras, several shrimp, 2 otos and some nerite snails is a high bio-load in a 20G tank, but not sure. Anyway, I have done zero water changes in over a month and my nitrates go to zero in about a week after fertilizing, so I believe my tank is healthy and not overloaded.

                  The only "disaster" on water changes in a non-CO2 that I know of is fluctuating CO2, because tap water typically has a fair amount of CO2 in it. Fluctuating CO2 can (and probably will) lead to algae. Personally, if I do raise my bio-load and get to the point of needing to do water changes, I will do the water change just after lights off in the evening and hope most of it is gone by morning when the lights come on. I have bio-wheel HOB filters on my tank, so I do not think there will be much CO2 left in the morning. I'm not sure if this will work, because it has not been mentioned here before -- seems logical to me, however.
                  Last edited by tedr108; 10-03-2008, 06:42 PM.


                  • #10
                    It sounds like you aren't doing that many water changes. I had quoted Carissa initially about the regular water changes. I forgot it was initially Carissa that I quoted because you had then replied so I thought you were following the same method.

                    I saw one mention here about doing the water change at night. Tom replied that although what you are saying makes perfect sense there are other algae causing factors besides co2 involved with a water change.


                    • #11
                      Well, if there are other algae-producing factors besides CO2 from a water change, I guess I'll keep the fish load low and avoid water changes. Thanks for mentioning that.