Ferts And Dosing Need More Info


I'm starting a new 5 gallon and will begin dosing on my 2.5 gallon. I've read a ton so far and this is what i've gathered. The more I read the more precise the information got and it's gotten to the point where I'm having trouble finding the answers to the specific questions I'm looking for. So I've come here. Obviously there are macro and micronutrients. Macro being most important, but micro needed too just not in the same quantity. If you find any information I just said that is wrong please let me know thank you

There's a general NPK ratio to shoot for:


I also heard of a Ca:Mg:K ratio as well:


And a NO3: Phosphate ratio:


I also read that there is a difference between nutrients that need to have a set level (ppm I'd assume). And ones that don't:

Ones that do: CO2, nitrate, potassium

Ones that don't: Iron, Phosphorous

Is that true?

For Nitrogen I should aI'm for 5-10ppm in NO3. I read that there's a NO3 and phosphate ratio too, of 10:1. So I can test my nitrate if at ideal ppm leave it alone. Then test phosphate, if I need to adjust should I adjust based on the ratio or the ideal ppm? That is, if nitrates are high should I dose to make my phosphate a little higher or shoot for that ideal range? From what I read I want to keep the nutrients balanced so I'm guessing aI'm for the ratio.

Phosphorous I heard conflicting things, some says ideal is .05ppm another said .1-1ppm. I heard too much phosphate interferes with metabolism of iron and disrupts the photosynthesis process. A test is available for me to guage how much is in my tank. So that's good. I suppose I can also ensure I have enough NO3 so that my plant won't be starved of one nutrient and not use the other. Does that ratio reflect a biological process they both share? or is it just a handy reference for the sake of just getting the numbers right?

For Potassium I read that potassium isn't gained from fish or plant waste and isn't in tap water so needs to be added. I heard 10-50ppm. Another website said 5-10ppm. A user on a forum posted that people typically dose 20-30ppm a week (I know that might vary widely from tank to tank). I also heard that potassium won't have the same effect as nitrogen or phosphorus on algae growth so I can be more generous. I assume I just follow the instructions to get to the ppm it advices. But how to know how quickly my plant life is going through it? There doesn't seem to be tests for it.

As for co2. An ideal level of 20-30ppm is generally agreed upon.

Magnesium I'm having a hard time with. A source said that over 10ppm is ideal. My water supply says that it has 6.09ppm so ineffecient if that +10ppm is correct. So I'm assuming I have to dose it. ALso, if those ratios are correct plants will use twice as much Mg as they do K and 40 times as much Mg as they do Nitrogen. Judging by that seems like I'll have to dose Mg a lot, but nobody every seems to talk about this specific one too much. I actually don't really remember seeing it a lot at all in conversations about dosing. What gives?


Concentration is more important than ratio. Plants have the ability to pick and choose what they need and will do just that. After having them for a while, you can test and see what your tank is lacking and adjust dosing from there. Nitrates aren't very important as plants prefer ammonia so if you have fish in the tank you shouldn't have to worry about them at all, unless you have a nitrate reducing filter system, then you might have to dose.
A lot of the ratios are more based on keeping water stable. Too much CO2 your ph drops too low, too much calcium, it rises too much etc. Keep your ph as stable as possible(it should swing a point or so, up to 2 in the course of a day with CO2 injection; no Lower than 6, no higher than 8 if your starting point is 7)


Not sure the exact ratios, you can get pre mixed bottles of macro and micro separately. You can start off low dosing and work your way up gradually, otherwise lots of testing and measuring. Have you looked at tnc complete and easy life pro fito? The ratios are there


Ratios really do not matter as much as concentration PER dose. It doesn't matter what the concentration is in your water (unless your water parameters are quite extreme).

IF you are using pressurized Co2 (not DIY or some liquid CO2 product), then here are some concentrations that you should aI'm for per dose, assuming each dose is performed 3x a week and a 50% water change at the end of the week.

Macro Dose:
7-8ppm NO3
2.5-3ppm PO4
K resulting from KNO3 and KH2PO4 should be enough

Micro Dose:
Use a trace mix like CSM+B and dose 0.3ppm Fe from the CSM+B

If you feel it's necessary to add more Ca and Mg to your water, you can add 1-2 dGH of GH booster once a week.

Use rotalabutterfly.com to help you determine the amount to dose in your tanks.

Similar Aquarium Threads

  • Question

Latest Aquarium Threads

Top Bottom