So I'm switching to EI. I went through the information available and created a dosing plan. Since my calculations are based on my 240g tank, I will focus on that. The provided sample dosing only went to 100-125g so I simply doubled that to get a dose of 1 Tbsp KNO3 and 1 tsp KH2SO4 three days a week and 1 tsp CSM+B on opposite days with nothing on Saturday.

I am only able to do a 20% water change on that tank at any one time due to the amount of water I can store in my tank from my RO unit so I was trying to figure out how many of those water changes I would need to do each week to keep things under control. I also have a 60g tank I'm using to grow out Discus fry and do near-daily 50% water changes so need to figure out how much more to dose to maintain the appropriate levels. I read some of the more detailed information about uptake of the various elements and attempted to produce a spreadsheet that would allow me to calculate it.

The calculated volume of the tank is 218g minus decorations, but I have a refugerium-style 20g tank I use for breeding and a bog that I pump water up into so I left it at 218g. According to Chuck's calculator, those dosages are 12.48ppm for Nitrates, 7.88ppm Potassium, and 4.06 ppm Phosphates. I guessed at approximate starting values based on what I was aiming for with PMDD. I found the uptake values from the thread in the EI section and picked middle of the range for those. To check my formula, I stuck wth the 50% weekly water change.

So my formula is:

(existing concentration * (1 - water change percentage)) + today's dosage - today's uptake

Assuming I've read things correctly, I'm supposed to dose that 3 times a week, but based on that and the numbers I've come up with, I'm looking at 30-50ppm Nitrates and 13-20ppm Phosphates which doesn't seem right at all.

I've attached my spreadsheet. The dosing plan is on the first sheet, the calculations are on the second sheet. At the bottom of the calculations I graphed it and got a graph that becomes consistent but seems to indicate very irregular concentration levels. But I did read that uptake isn't really constant, so that much may not be important. My bigger concern is that I'm massively overdosing my tanks. I've only been at it for 3 days so I don't think I've done any damage yet.

Michael