# Are my liquid ferts too weak?

I recently have been having some plant issues so I decided to track my nitrates over time so I can see if my plants are using it up too quickly and being deprived of nitrogen/other nutrients in the ferts. I ran some calculations to see where my nitrates would peak before plants start uptaking it just to know how far along in returning to a baseline I am.
My fertilizer is 2.64% Nitrate = 26400 ppm
Add 6 mL of this fertilizer into 250035 mL (55 gallons)
The increase in nitrate caused by my ferts is only 0.63 ppm. My starting nitrates at the beginning of the week is 5 ppm and I know from previous testing that it's 5 ppm a week later before I do my water change. I know most NPK liquid ferts don't go much higher than 3% nitrogen, so it's very hard for me to achieve the minimum 20 ppm good for plant growth.
Does my math check out and is this normal?

brhau
Are you sure the ferts are not 2.64% Nitrogen (as opposed to 2.64% Nitrate)? That seems more likely for an all-in-one. In that case, the molar mass of nitrate is about 4.4x that of nitrogen, so 6 ml of fertilizer adds 2.79 ppm NO3. If you take into account the dead volume in your tank, it might be more like 4ppm.

You can either increase the fert dosage or add KNO3.

Cheers

Are you sure the ferts are not 2.64% Nitrogen (as opposed to 2.64% Nitrate)? That seems more likely for an all-in-one. In that case, the molar mass of nitrate is about 4.4x that of nitrogen, so 6 ml of fertilizer adds 2.79 ppm NO3. If you take into account the dead volume in your tank, it might be more like 4ppm.

You can either increase the fert dosage or add KNO3.

Cheers
Yeah 2.64% nitrogen but still if you just do a simple dilution calculation there's barely any difference. I didn't include molar mass in the calc just M1V1=M2V2. Even 3-4 ppm is barely anything.
EDIT: Oh I think I get what you mean, so 2.64% nitrogen is actually something like 10% nitrate? That's a weird way to represent that haha

brhau
Yeah, they advertise 1 ml/ 10 gal = 5ppm nitrate. Unless my math is also wrong, the actual numbers seem to be about half that.

Yeah, they advertise 1 ml/ 10 gal = 5ppm nitrate. Unless my math is also wrong, the actual numbers seem to be about half that.
Probably going to up it a bit, I imagine if nitrates are that low below the 20 ppm minimum that people like to shoot for, my other nutrients are low too

RayClem
Do not make the assumption that if your tank is low in nitrates that it is similarly low in other nutrients. That might be the case, but it might not. The all-in-one fertilizers are typically designed to provide an excess of nutrients which is kept under control though large, frequent water changes.
There are also specific nutrients that can be added based on the appearance of your plants. A lack of a specific nutrient such as nitrogen, phosphorus, potassium, iron, calcium, or magnesium has specific symptoms. Some tanks have sufficient nitrogen and phosphorus, but are deficient in potassium. If you have a lot of plants, you might be low in nitrogen. You need to examine your plants and figure out what they need and then provide it. If you decide to go the all-in-one route, be sure to keep up with the water changes.

Do not make the assumption that if your tank is low in nitrates that it is similarly low in other nutrients. That might be the case, but it might not. The all-in-one fertilizers are typically designed to provide an excess of nutrients which is kept under control though large, frequent water changes.
There are also specific nutrients that can be added based on the appearance of your plants. A lack of a specific nutrient such as nitrogen, phosphorus, potassium, iron, calcium, or magnesium has specific symptoms. Some tanks have sufficient nitrogen and phosphorus, but are deficient in potassium. If you have a lot of plants, you might be low in nitrogen. You need to examine your plants and figure out what they need and then provide it. If you decide to go the all-in-one route, be sure to keep up with the water changes.
yeah I do about a 50% water change every week, good for adding CO2 rich water too. My plants are fine the roots are the issue. I have a huge floating water sprite plants that primarily use atmospheric CO2 so I imagine they're what's keeping my nitrate so low. I don't have algae problems except for some brown hair algae that grows within the water sprites and a little bit on my driftwood near the surface, so I could probably increase ferts safely.

brhau
It might be cheaper to buy some KNO3 and selectively dose that, but I'm sure upping the all in one would also be fine. The whole concept of EI is to add excess nutrients so nothing is limiting, and remove them with water changes.

It might be cheaper to buy some KNO3 and selectively dose that, but I'm sure upping the all in one would also be fine. The whole concept of EI is to add excess nutrients so nothing is limiting, and remove them with water changes.
I may invest in a phosphate test or go to my lfs to see where other nutrients are at then make my own ferts if necessary, thanks for the help!

RayClem
You might consider using Seachem Flourish Nitrogen fertilizer. It contains potassium nitrate and urea. It contains no free ammonia. Because it contains potassium nitrate, it increases the potassium levels as well as nitrogen. Many tanks are low in potassium, so you might find it useful.

Many people think Seachem Flourish Comprehensive is an all-in-one fertilizer; it is not. It contains primarily micronutrients. It does not contain sufficient levels of nitrogen, phosphorus, or potassium. That is why Seachem offers fertilizers with the specific macronutrients.

You might consider using Seachem Flourish Nitrogen fertilizer. It contains potassium nitrate and urea. It contains no free ammonia. Because it contains potassium nitrate, it increases the potassium levels as well as nitrogen. Many tanks are low in potassium, so you might find it useful.

Many people think Seachem Flourish Comprehensive is an all-in-one fertilizer; it is not. It contains primarily micronutrients. It does not contain sufficient levels of nitrogen, phosphorus, or potassium. That is why Seachem offers fertilizers with the specific macronutrients.
I think their NPK series nitrogen is only 10,000 ppm but my current is 26,500. Even the Thrive people rave about is only 3. Perhaps I'll use the seachem if it's just nitrogen but if my other nutrients are low it becomes tougher.

Rotala Butterfly | Planted Aquarium Nutrient Dosing Calculator

This online calculator for ferts is very helpful to determine dosing requirements. Also I would recommend getting the Salifert nitrate test kit it has better resolution.

I got it because the LFS was out of API test kits.
Speaking of nitrate test kits, I think my API one is no longer working properly. I have dosed 6 mL of ferts every night for 3 days and I haven't got my nitrates to budge from <5 ppm. I used a spectrometer in my lab to see if the test kit was working and there was no change from just adding the test solutions to nitrate-free water (not tap). When I made a very strong solution of sodium nitrate (well over 160 ppm), I only got a color change equal to 10 ppm nitrate (using values from here). So likely going to need to buy a new kit anyway.
On the other hand, a few of my moneywort stems rotted overnight so I'm really not sure what my problem is.
EDIT: also for some reason that link you gave me uses only iron as a benchmark

Plantedtank2021
Need to play a round with the calculatetor. I am relatively new to planted tanks but I have a chemistry background … but no access instrumentation.
The Salifert kit keeps reagents separate. API does not, hence the shaking.

If you have a low tech set up and moderate fish load I do not think most if not all nutrients should be covered.

I had a tank with high biological load and a hornwort and Frogbit. I only added Seachem Comprehensive. Did not have nitrates reading over 5 ppm and everything grew like crazy.

I was using the API test kit then an would do one at 100% tank water and 50% tank water 50% RO water. This because API kits are hard to read at higher ppm.
I meant most if not all nutrients should be covered in low tech with moderate bio load

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