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900 planted gallons H2O: Fish waste have everything my plants need?

898 Views 2 Replies 2 Participants Last post by  Oreo. Niloticus
Hello. I am a first time aquarium keeper. Yet, I've gotten into planted tanks in a big way in a hurry… all of which started by getting 150+ Red Nile tilapia fry in late June.

This, however, is a plant question regarding whether additional nutrients are necessary for the plants for me to put into my soilless systems besides what is produced by the fish waste if I don't do water changes. I thought fish waste had everything.

My plants that are not in soil are becoming lighter and lighter green and not growing as well.

My many plants are mainly pickerel rush, lanceleaf arrowhead, cattails, dwarf papyrus and lots of water hyacinth.
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A test kit will go a long ways towards helping determine what if anything needs to be added, nitrate phosphate potassium (NPK ) are the macro nutrients plants need to thrive, test kits are available for phosphate and nitrate, though a hobbyist level test for potassium isn't available, though the general consensus seems to be it's not needed.

After that, if you decide based on additional reading that you need to dose nutrients, you can buy dry fertilizers (or wet, but dry are WAY cheaper for the volume you'd want), there are lots of variations to the chemical structure's of the ferts, depending on how you want to fine tune things (if you get so far) nitrate is generally kno3, phosphate is generally kh2po4, and potassium (if you really really actually need it) is k2so4, though the kno3 and kh2po4 both add some potassium already. Some of the other commonly dosed minerals are calcium, magnesium, and iron, with trace minerals rounding out the bunch (rare earth metals, and the like in very very small amounts, and again usually not needed unless you have a specific reason). These dry ferts are prefered over say a commercially available hydroponic mix, because you can fine tune what ratios you want for your plants based on observed usage from testing

As to the lightening of the green in the leaves of your plants, some of that may be attributed to the intensity of the light they are now receiving vs how much they would get if grown in full sun outside. It can also be a nutrient deficiency (usually nitrogen) though would probably require pictures and someone a bit more practiced in identifying deficiencies to chime in.
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Thank you for your reply Theatermusic87. I really appreciate it.

I deleted a lot of my outloud thinking from earlier. My current theory is that the nitrate is high, and the plants don't know what to do with it all, so they are becoming lighter to reduce photosynthesis. Perhaps the stripping of other nutrients from the water due to the lack of water changes, (or lack of nutrient supplementation), contributes to the plants inability to use nitrate.

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