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Feeding plants

Discussion in 'New to the Hobby Questions and Answers' started by Ingrid, Aug 19, 2019.

  1. Ingrid

    Ingrid Fish Fanatic

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    How often do you need to feed plant in a fish tank ?
     
  2. Colin_T

    Colin_T Member

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    If you use an iron based fertiliser, you can monitor the iron level with an iron test kit and keep the iron level at 1mg/l (1ppm). If the iron level drops bellows 1ppm, you add a bit more fertiliser to bring the level back up to 1.

    If you don't add fertiliser, then just feed the fish and give the plants some light and don't worry about it unless you get heaps of algae.
     
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  3. Byron

    Byron Member

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    This takes some explanation.

    Plants grow by photosynthesizing. In order to photosynthesize, there has to be sufficient light (intensity and spectrum factor in) along with the necessary 17 nutrients in sufficient quantity to balance the light. And each species of plant has its own specific requirement for this balance; fast growing plants require more, slow-growing plants less, generally.

    Light is thus the most crucial factor, as it must be of a certain intensity and spectrum to drive photosynthesis. Duration does not compensate for inadequate intensity/spectrum. So assuming the light is "OK," we can consider the nutrients which is the substance of your question.

    Fish excrete all the nutrients plants need. There is also the breakdown of organics primarily in the substrate which adds more (especially the CO2). Water changes replenish the minerals (except obviously in very soft water) as well as removing substances that are detrimental to plants and others detrimental to fish. Depending upon the plant species and numbers, the light, and the fish load, some plants will manage very well just from the aforementioned.

    If it is necessary to supplement any of these nutrients, it is important to do so with a balanced "fertilizer." An excess of some nutrients can cause plants to shut down assimilation of certain other nutrients; the excess can also feed algae because algae is not as fussy as higher plants over light and balanced nutrients. This is why comprehensive supplements are best; they provide what the plants need as a supplement to what will naturally occur in the aquarium, but the nutrients are in specific proportions to each other. Algae is much less likely to take advantage, because the plants are able to use what is being provided...again assuming everything is basically in balance.

    Some plants benefit from substrate supplementation with products like Flourish Tabs as opposed to a liquid fertilizer. The real benefit here is that the plants can utilize the nutrients as needed while the nutrients are not just released into the water where algae may use them.

    Comprehensive supplements include Seachem's Flourish Comprehensive Supplement for the Planted Aquarium, and Brightwell Aquatics' FlorinMulti. These are two I have looked into and used, but I'm sure they may be others. However, do not resort to individual nutrients; usually this is not going to benefit because it throws the balance out. The complete supplemental products contain what is needed in proportion as needed by plants, so unless you overdose (or under-dose), algae is not going to benefit.
     
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  4. Ingrid

    Ingrid Fish Fanatic

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    That was very helpful and informative
     
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  5. Byron

    Byron Member

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    Thank you. I just realized I forgot an important aspect, and that is the impact of liquid fertilizers/additives on fish. While it may be necessary to use a comprehensive liquid (I do in all my tanks because substrate tabs are useless in providing nutrients to floating plants and those not rooted in the substrate) we must keep in mind that these do get inside the fish and keeping them minimal is important. Overdosing plant fertilizers, just as overdosing medicine, rarely benefits but usually makes things worse.
     
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  6. Back in the fold

    Back in the fold Fishaholic

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    I really like Colin's suggestion for when you don't use fertilizer. I have never had anything other than low light plants and following that advice have had my plants do reasonably well. Got to watch room light from windows though. You will see a couple pictures on these forums where algae really took over.
     
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  7. seangee

    seangee Member

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    To follow up on what @Byron said about liquid ferts. Many people on here (myself included) seem to do well at half the recommended dosage.
    Personally I keep plants to benefit my fish rather than the other way around. For that reason I won't use CO2 or other substances that can harm my fish or shrimp (an example is the so called liquid Co2 which is actually poisonous, but great for plant growth). Different plants do have different requirements. If a particular plant plant fails to thrive in a tank I don't try to change it to suit the plant. I throw out the plant and plant something that does well in that tank. In my case that means different plants in different tanks because each tank is a unique, and different environment in terms of lighting, nutrients and CO2. And that means plants with modest light requirements, because all of my fish do best in subdued light.
     
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