Ooo , ok and another
Quoted from
@Freshflora
“targeting about 18 - 1.8 - 24.”
So if I am targeting a certain amount in the water column how do I begin understanding how to determine what number I’m targeting based on my weekly totals ?
Directed at no one specific just a general question.
The simple answer is for each parameter of dosing, the equation is [the weekly dosing amount] / [the percentage of water changed weekly expressed as a decimal].
let’s just take your weekly dose in nitrates, which is 9. And let’s assume you’re doing 1 weekly 50% water change so it’s simple. The math for your water column target for nitrates accounting for accumulation is 9 / .5 = 18.
In your case now, you’re doing 2-3 weekly water changes of 50%. If you remove half of the water the first water change of the week you’re still left with 50% of the original tank water and you’ve added 50% new water. You do another 50% water change and now you have 25% of the original tank water and 75% new tank water. If you did another 50% water change, you’d be left with 12.5% of the original water you started with that week, and you’d have replaced 87.5%.
So if you’ve done 3 50% water changes in a week, you’ve replaced 87.5% of the water. As a decimal, that’s .875. So to find your target for nitrates you would divide 9 by 0.875 = 10.3 (rounding to the nearest 10th).
If you do 2 50% water changes a week you’ve changed 75% of the water. So the equation would be 9 divided by .75 = 12.
One main takeaway from this is that your water change schedule affects your dosing, and that’s an important reason why you should stick to a consistent schedule as much as possible. It’s better to consistently stick to a specific water change schedule rather than some weeks 2 and others 3 and others 1, because you’re changing the dosing parameters by doing so which plants do not like. Plants love consistency. Of course there are times you need to step up water changes from once a week or slow down, and that’s okay, but you shouldn’t be constantly switching up how many water changes you do weekly if you want happy plants.
Another important thing to understand is the “target number” assumes that plants are not uptaking any nutrients. In order for there to actually be any accumulation, you have to have some amount of nutrients left over in the water column by the end of the week. So for example if you had 2 little fish in your 60 gallon tank and you were dosing 1ppm nitrate a week and it was densely planted, it would make no sense to seriously talk about the target number because the plants are probably just sucking up that 1ppm.
One reason I bring that up is because with your weekly amounts, you may not have much accumulation at all. Dennis Wong says all the time in his APT Complete dosed tanks that his nitrates measure 0-5, and he doses around 7ish nitrates a week with APT Complete. The idea of accumulation and “target” dosing numbers come originally from the EI dosing methodology, which aims to have nutrients in some amount of excess, so most often people who use the target numbers are also operating under the EI or an EI adjacent methodology. But it’s also a helpful way to convey to people your dosing and your water change schedule simultaneously.
