Stable nutrient dosing using hobbyist test kits

[Dennis Wong]

This is an extension/excerpt from the longer nutrient stability article and why it matters :

Why nutrient level stability matters for planted aquariums

Nutrient stability in planted aquariums - how to have stable nutrient levels and why it is important. Avoid triggering algae and tip stunting.

www.2hraquarist.com

I have added a portion and simple guide for folks that are using hobbyist test kits to dial in their levels:

To have stable nutrient levels, the goal is to have the same visual shade of color when using a nitrate test kit on your aquarium at any time of the week.

To do this, you need to start by having a stable method of dosing nutrients daily. By testing to see whether nutrients build up or deplete across the week, you will know whether your daily dosing rate is higher or lower than your tank's uptake rate of nutrients.

To do this, take measurements using the test kit across the week. Take the pictures in a fixed location and store the pictures on your phone or computer to use as color comparisons for readings across the week. If your nitrate tests show lighter colors at the end of the week compared to the first day of the week, it shows that your dosing rate is lower than your aquarium's uptake rate. In aquariums where the difference in uptake and dosing rates is small, the difference may only be seen by comparing the colors on the first and last days of the week. In aquariums where the daily dosing rates differ significantly from the uptake rates of the aquarium, a color difference may be seen by mid week.

A dropping nitrate test reading at the end of the week indicates that daily additions of nitrogen are less than what the aquarium uptake rate is. In such a scenario, you should increase your daily dosing slightly to maintain stable levels. For slight differences in color (less than 5ppm), you increase your dosage by just 0.5ppm Nitrate per day. For color differences larger than 10ppm, try increasing it by 1ppm Nitrate per day.

A rising nitrate test reading at the end of the week indicates that daily additions of nitrogen are more than what the aquarium uptake rate is. In such a scenario, you should decrease your daily dosing slightly to maintain stable levels. For slight differences in color (less than 5ppm), you decrease your dosage by just 0.5ppm Nitrate per day. For color differences larger than 10ppm, try decreasing it by 1ppm Nitrate per day.

If you are using the EI dosing approach, water change day is used to reset nutrient levels. One way to hit your target saturation level on the spot without the use of test kits is to change 100% of your water and dose exactly the amount of ppm in nutrients you want. i.e. 100% water change, dose 15ppm NO3, boomz, guaranteed 15ppm of NO3 in the water column.

If you are doing say a 50% water change, and your water has 20ppm of nitrates before the water change, you would want to dose back 10ppm of nitrates back to keep nutrient levels stable at 20ppm. If your target level is 15ppm of nitrates instead, then after a 50% water change (removing 10ppm from 20ppm), you will need to dose back 5ppm of nitrates instead. Over the long run, the goal should be to keep levels the same before/after water changes.

If instead you are using the zero bound approach to nutrient dosing, then the goal is to just keep nitrates at 5ppm and below after water changes. If nutrients levels have spiked significantly during the week, say it is at 10ppm now, then just do a larger water change (80-100%).

 

[Calamardo Tentaculos]

Thank you @Dennis Wong ! Given the inaccuracy of most hobbyist test kits. Are there any brands other than Hanna that are okay-lah, to use Singapore parlance.

 

[Pepere]

I have found that on some test kits such as the API liquid test kit it can be hard to discriminate between certain color swatches. 10 and 20 ppm look annoyingly the same.

To overcome this I do a base test and a 50% dilution test. Ie, I mix a quarter cup of tank water with a quarter cuo if tap water and test this diluted sample. If the second test is exceedingly closer in color to the first I conclude the tank is sitting closer to 20 ppm. If however the second test looks a lot closer to 5 ppm swatch then I conclude the tank is sitting closer to 10 ppm nitrate.

 

[Dennis Wong]

Thank you @Dennis Wong ! Given the inaccuracy of most hobbyist test kits. Are there any brands other than Hanna that are okay-lah, to use Singapore parlance.

There are some China side test kits that test for a narrow range, i.e. 5-40ppm,. and they give easier color matching. I came across them a couple of years back so I don't remember their names, but if you check china online shops like taobao/aliexpress they are there I think.

 

[Mitelog]

If i can give advice for good and accurate test kit for nitrate and phosphate : Red Sea !

They are a reef brand but i tested those 2 for freshwater and they are easy to read and narrow range !


Like Rocco have already said, the salifert are very good too and cheap ( at least in Europe)

I myself use the Hanna checker No3 and Po4 and with them i know exactly what nitrate is consumed per day.

Unfortunatly for the phosphate, due to my aquasoil « eating » them more rapidly than lukyluke pull out is gun i can’t apply the principle that Dennis advice here for a stable level.

 

[hamfist]

I have found that on some test kits such as the API liquid test kit it can be hard to discriminate between certain color swatches. 10 and 20 ppm look annoyingly the same.

To overcome this I do a base test and a 50% dilution test. Ie, I mix a quarter cup of tank water with a quarter cuo if tap water and test this diluted sample. If the second test is exceedingly closer in color to the first I conclude the tank is sitting closer to 20 ppm. If however the second test looks a lot closer to 5 ppm swatch then I conclude the tank is sitting closer to 10 ppm nitrate.

Very true. My eyes literally cannot see any difference between the 10 and 20 ppm colours on the API nitrate test colour chart. Doing a 50% dilution test is a clever option, and is certainly really very useful in some situations. You are clearly doing this ina n intelligent way.
I have gone the route of using the Salifert nitrate test as I find it reliable and my eyes can tell the difference between the colours much better. Maybe my eyes find different shades of pink easier to distinguish between than different shades of orange.

@ Dennis Wong ............. using nitrates as the parameter one is trying to keep stabilised during the week. Just as a guestimate, what do you think would be a reasonable range of weekly nitrate swing without the plants really noticing ? I think I'm reasonably successful at keeping mine as steady as possible with daily dosing but, even so, I know that as the tank evolves and changes, nitrate-appetite changes and I can have up to a 5ppm swing (mean daily average nitrate of around 10 ppm) during the week.