Originally Posted by Michael Hoaster
Let's discuss dosing-for planted tanks. It's really just a fancy word for feeding. Like reef tanks, planted tanks require food. Plants consume a number of nutrients, and will strip them from a closed system in short order. Unlike reef tanks, where aquarists struggle to keep nutrients low, planted tanks require their keepers to maintain higher nutrients. It's rather a huge difference and calls for a huge change of mindset. We don't want to starve our systems, we want to fatten them up!
Plants can get all the nutrients they need from fish food alone. The only problem is the ratio of nutrients from fish food is not ideal for plants (or closed systems). Dosing addresses this problem.
So what do we dose? Mostly, it's the macro nutrients-the ones plants use a lot of. These are Carbon, Nitrogen and Phosphorus. The ratio of these is important. The average C-N-P ratio for seagrasses and macro algae is about 550-30-1.
With phosphorus being 1, we don't need to dose it. We get more than enough, just by feeding the fish. The exception would be a tank with no fish to feed. Then you would need to dose it.
Nitrogen is 30. That's thirty times MORE than Phosphorus. Big dif! New tanks naturally generate a lot of nitrogen during the Nitrogen Cycle. As the biological filter matures, bacteria consumes nitrogen, in the form of ammonia, nitrite and nitrate. So, biological (bacterial) filtration competes with plants for nitrogen. Nothing we can do about that, except we can deemphasize it by not adding anything specifically to 'help' it. So bio balls or other biological media are not needed. Nitrogen, in some form, will need to be dosed. One of the safest forms for aquariums (closed systems) is Potassium Nitrate, sold as stump remover at hardware stores. One of the riskiest forms is Ammonia. Why would anyone willingly dose Ammonia? Because it is plants' preferred form of Nitrogen. Plants have to work harder to use Nitrate. The danger is that Ammonia is also micro algae's favorite form of Nitrogen, so you run the risk of algae blooms, especially in smaller tanks or tanks with fewer plants. So stump remover is recommended, and ammonia is use at your own risk, and best left to larger, more heavily planted tanks.
At 550, Carbon is the big one. Plants need it more than ANY other nutrient. In nature and in aquariums, it is most often the limiting nutrient for plants. Carbon Dioxide (CO2) is plants' preferred form of Carbon. Many fresh water planted tank keepers dose CO2, to get luxurious plant growth. It is just as helpful for marine plant keepers. A simple way to dose CO2, is to rent a 5 lb CO2 tank, top it with a regulator, and run airline tubing to the intake of a pump or a canister filter or reactor. If you already have a calcium reactor setup, you're good to go. For some reason, people seem to shy away from CO2. I don't know if it's the perceived complexity or the fear of exploding CO2 tanks. So the number one most important plant nutrient is often ignored! If I was told I could only dose one thing, it would be CO2.
The micro nutrients are ones that plants need in much smaller quantities. But, in our closed systems they get depleted too. Water changes alone can replace them, but the beauty of planted tanks is that they don't need frequent water changes, and dosing is easier. The one that gets used up the fastest is Iron. I use an iron supplement made for fresh water planted tanks. Calcium is also needed by plants. I add calcium media to my (CO2 injected) canister filter, to get a quasi-calcium reactor. For everything else, I use a trace element supplement, fish food and occasional water changes.
That's pretty much it, for the plants. I dose a few other things for other organisms. We'll discuss that next.
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