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Do plants always need fertilizer, Micronutrients and Macronutrients

maverick786us

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Columbus, GA
A 3 months old heavily planted cycled tank, that has pressurized CO2, and fish waste and uneaten food is food source for plants (ammonia from it broken into nitrates), do plants always need fertilizer, Micronutrients and Macronutrients to consume nitrate and CO2?
 
They need nutrients one way or another, yes.

There are many potential sources of nutrients besides fertilizer (tap water, fish waste, soil, certain rocks), but all these sources are highly variable and can be hard to quantify. Some nutrients are harder to come by through these routes than others. How can you be sure your plants are getting enough of all the different elements they need? The more plants you have and the faster they grow, the more nutrients they will need. Most of us add fertilizer to be sure we have all of our bases covered, though there are many different approaches about how to do that.
 
OK initially I thought a fully cycled planted tank get its nutrients from fish waste and uneaten food. Then one day I was shocked when I discovered that, my 3 months old heavily planted tank had nitrate level bit high. I did my research and I got questions from some of the experts, that how frequently do I dose fertilizers, nutrients (micronutrients and macronutrients) to these plants. The experts said that plants need those doses to CONSUME nitrates and CO2. I was bit puzzled that nitrate is already a natural fertilizer / food for plants and the plants need extra bit of nutrients to consume their basic food?

Regardless I increased the dose of fertilizer and nutrients (micronutrients and maconutrients ) to twice a week. But somehow I felt it wasn't adequate for the plants, because I didn't see the plants develop vibrant color, it was a non CO2 tank, but I was using liquid CO2, I thought its a substitute to pressure injected CO2.

One day I met a guy who is into aquascaping and he made some really good aquascape with carpet grass and background plants. I asked him which fertilizer, and nutrients formula he is being giving to his plants. He said he as 5 massive sized tank (50 gallon) and for such a large quantity of water it will cost him a fortune for fertilizer and nutrients. He said he let plants get nutrients naturally from fish waste and uneaten food.

So let me rephrase my question. Without fertilizer, nutrients (micronutrients and macronutrients), from external sources the plants will not consume nitrates and CO2 at all?
 
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The easiest way to look at it is if you think of it as a balance. For proper plant growth you need all the building blocks in a particular ratio and that means if you have an excess of one it isn't being used up because you are limited by the amounts of the others. This is why we dose nutrients, so that plants aren't limited by one of these building blocks. Some nutrients are abundant because of high stocking levels, large amounts of food etc but others are not added in the quantities healthy plant growth needs unless we intervene.

Liquid co2 doesn't compare to injected co2 but many plants don't need either, you just limit the speed of growth. Lots of us aren't co2 users and you can maintain a very healthy, largely problem free tank without it.

A high fish load and heavy feeding can certainly maintain a planted aquarium, it was what I did for years, but it does limit the species of plants that will do well. It tends to be the very weedy or easiest of plants that don't need any addition but many plants just won't do well in such an environment.
 
was shocked when I discovered didn't see the plants develop vibrant color, it was a non CO2 tank, but I was using liquid CO2, I thought its a substitute to pressure injected CO2.
"Liquid CO2" does have its uses but a substitute for injected CO2 gas is not, misleadingly, one of them. The liquid carbon is a good algaecide, particularly applied neat on hardscape, but it won't meaningfully affect carbon levels as a plant growth limiting nutrient.
 
If your tank is so unhealthy for your plants that they stop growing, yeah, at that point they won't be taking up nitrates or CO2. If they are growing at all, they are consuming some, though the amount will be less than if the plants weren't being growth limited.

As with so many things in the hobby, you have to look at your system as a whole. The high nitrates in your water column doesn't mean that your plants aren't consuming any, just that they are being produced at a faster rate than the plants are using. Maybe your plants are growing well, but you have a lot of fish and don't do many water changes. That could result in high nitrates, and it would be more easily remedied with water changes rather than messing with the plants. Plants that have access to the air are sometimes called "nitrate sponges" because they grow so fast they can use a lot of nitrogen.

Some people have a system that doesn't require extra fertilizer, but their plants are getting all their nutrients from other places. These tanks tend to be a specific flavor of tank - no co2 injection, lower light, light fish loads, lots of easy plants. Everything is low demand and slow growing and it's easier to keep in balance.

One day I met a guy who is into aquascaping and he made some really good aquascape with carpet grass and background plants. I asked him which fertilizer, and nutrients formula he is being giving to his plants. He said he as 5 massive sized tank (50 gallon) and for such a large quantity of water it will cost him a fortune for fertilizer and nutrients. He said he let plants get nutrients naturally from fish waste and uneaten food.

If he's found a way to make this work, then that's great, and if you want to follow his method you'll need to copy them as closely as possible. But if you learn to you dry salts fertilizer isn't especially expensive, especially compared to everything else in the hobby. It just requires some research and math.
 
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