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Fish really we need them?

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  • Fish really we need them?

    Well I Have Aquariums without fish and aquarium with fish. I dont fertilize regulary and i see that the aquarium with fish the plants do great. So really fish can be used like a fertilizer maker? I thought that fish only makes algae problems.

  • #2

    Hi Brian,

    Fish provide a wonderful service in planted tanks by causing us to feed them (add fertilizer), help breakdown food into more usable forms and providing carbon dioxide.

    I have a number of fishless tanks and ‘grow out’ tubs. The advantages of fishless planted tanks are that I can crank up the CO2 and add far more fertilizers, without worrying about harming the critters.

    Yes, if you have fishless planted tanks you need to add nutrients.

    The first sign we don't know what we are doing is an obsession with numbers. - Johann Wolfgang von Goethe

    Disclaimer: I am not trying to make you mad, it is just what I am, an evil plant monster, 'nuf said.
    • I believe the information I am giving is sound, I am not a veterinarian, professional chemist or particularly bright and certainly not a "Guru.".
    • I assume you are of legal age, competent and it is legal for you to acquire, possess and use any materials or perform any action in your in your jurisdiction.
    • When in doubt "don't."


    • #3
      Fish eat food, convert the N in food to NH4 (sometimes NH2(2CO) which converts to NH4 when it hits the water), the nitrification cycle kicks in and the NH4 is converted to NO2 then NO3. From one end of the stage to another there's a nitrogen based compound that plants can use. Even excess food will convert to ammonia, and the cycle will start in. Some people fishless cycle their non planted tanks with fish food; not the greatest idea, but it works.
      Last edited by Philosophos; 12-08-2009, 05:30 PM.
      - Dan


      • #4
        The idea that fish add fertilizer => which is then used by plants for growth and removal of waste is an old idea and one very popular with aquarist going back to the inception of aquarium keeping, and it's still often a goal for many aquarist.

        Fish waste is not the best balanced food for plants however, but it can still get the job done very well at lower light, or where sediments that are enriched(which no longer means the nutrients are all from the fish anymore) ***and or*** water column supplements.

        It certainly can work fairly well without any fish, and likewise, fish can help out a lot if not mostly.

        Depends on the light, CO2 and plant species in question, not all plants will respond as well.

        Tom Barr


        • #5
          In a 55G Echinodorus tank I have a enriched substrate and the plants looks great for that. But not fertilizing the water sometimes the waters gets unbalansed in new tank and cause algae, then I make a w/c and add N, K, micros and the other day P and the algae disminished a lot. Im making this a long time ago. I know that the fish make food for plants but im asking if we really need fish with certain plants, because in fishless tanks some plants dont do well, and the same plants grows like weed in a tank with fish, **Only observation** My hipotesis is that the fishes can actually works like a slow relase nutrients for plants that in fishless tank can have a lack of nutrients in short periods but significantly damages the plants.


          • #6
            Certainly, I fully agree.
            The old " better some than none" approach.

            This is a good argument for having a good fish load.
            The other might be no need to dose any NH4 for plants.

            A third might be simple forgetful, neglectful aquarist habits!
            Like adding nutrients to the water column and sediment, it provides a 3 rd level of redundacy for a source of nutrients.

            If your plants did poorly in fishless tanks, that was still your/human dosing issue. That can be mimics, but you have to dose or add sediment NH4 which will only last so long before more is needed.

            All plants do very well without any fish however.
            I know of no plant that needs fish waste or NH4 dosing.

            They all can do well on KNO3 etc.

            So while I agree with fish adding more to the aquarium, if you go the other way, then dosing more will be required without fish.

            But most aquarists, and that is why I still call them aquarists, have fish.
            One of main features and focus, however, many lose sight of that getting into plants.
            I prefer a balance of interest and genres.

            Makes for a more well rounded aquarist that way.

            Tom Barr


            • #7
              well, Im more focus in plants than fish, Really now all my plants are doing well in the fishless tank, only a algae bloom (the tank have 1 month or less) I will make my trick again to get rid of the algae. I agree with you Tom I think maybe some plants do better in fish tanks because they never depletes their "food" because fish are making "food" for plants 24/7. In a fishless tank If you not are checking it all the days maybe one nutrients like Phosphorous or Nigrogen gets depleted and If you dont know and no fertilize the water column the plant can die.


              • #8
                Well, I think it's more useful ,to think about ferts/fish/sediments as a continuously changing.
                As they change there is some delay in the plant growth response.

                It's not this on/off response, it progressive.

                Regions A is not what most suggest, but for some nutrients, like say PO4, this is still okay.

                Regions B is the "leaner crowd", some moderate limitation is still okay and often does not harm plants too much, but that range is small and takes a lot more management to achieve(often missing the larger factors involved like CO2/light management).

                Region C is the critical range, or just enough to maximize growth.

                Region D is more along the range of EI dosing.
                It's broad and easy to hit that range.

                If you have a case say where you are in the A or B range, then fish will offer a back up that you may very well require.
                At C and D, not so much.

                Tom Barr


                • #9
                  Thanks Tom!!! I can post the graph on my forum?


                  • #10
                    Sure thing, it's more useful than trying to talk it with words

                    Tom Barr