Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Todd, each set up is a custom project.
You need to know...
A) ... your goal:
If you are running a high tech tank, then you will highly likely be fertilizing pretty heavily with all the ferts and traces. No matter what water you start with, no matter what substrate, you will be adding ferts.
If you are running a Walstad, or low tech set up then you might find your substrate, fish food and tap water supply most or all the fertilizer needs, so you may not need to supplement at all.
B) ... what you are starting with:
If your tap water is pretty decent then keep it and include the minerals in your figuring as part of the nutrient supply. (Usually this means GH and KH)
If your tap water has things you do not want in the tank, then go with RO or whatever it takes to remove the toxins. Or a blend of RO and tap to suit the fish.
A high quality substrate may start with some fertilizers, so you might have to alter your fertilizer recipe as the substrate ages and gets depleted. Hopefully you are fertilizing to keep the substrate fertile, not wait until it is depleted.
A high quality substrate has good cationic exchange capacity, so some variations in fertilizing are OK. The substrate acts like a cushion so the nutrients are more evenly available to the plants.
If you are using sand or gravel, no nutrients, no CEC then your fertilizer dosing might be different.
C) ... other sources of plant nutrients:
Fish (or shrimp or frog) food is the other biggie. If you are keeping a big school of something, plus a shoal of bottom fish, then fish food is a significant amount of N and P, plus many trace minerals. If all you have are a few shrimp, then this is a tiny source. Note that the N does not come from the fish, it comes from the fish food. The fish digest it to transform the fish food into fertilizer, but you could just dump fish food into a tank without fish and bacteria would turn it into (expensive and messy) fertilizer.
Decomposing organic matter supplies CO2. Not much, and not very fast, but it may be enough for a low tech set up.
So... here is how it has worked for me over time:
More fish than plants, poor light, no added CO2, gravel substrate.
I could only keep the most durable of plants, and the fish ate half the plants.
I got rid of the fish that ate plants, and moved the tanks nearer windows. I added K and Fe (Leaf Zone). I also added Excel. Plants did best in tanks with a little direct light, showing me that I sure did not have enough light. Plants grew just fine in the gravel, but it was not really what I wanted in the tanks.
I doubled the light, and moved the tanks even closer to the windows. I started trying different substrates, finally found Soil Master Select.
I started the full EI method, and used DIY/yeast CO2 and Excel.
Plants still did not do great, but a lot better than before. At least I could keep plants in all the tanks. I adjusted the EI dosing based on water tests. I was adding too much nitrogen (My tanks were still pretty well stocked with fish).
I am just getting started with a greenhouse roofed fish room. Now I have PLENTY of light! Algae is thriving like nobody's business. Some plants are doing OK, too. I need to get the CO2 running again, and start dosing ferts. Fish population is way down.
Here is how I figure the fertilizer: (based on scenario 3 above. I have yet to re-figure for scenario 4)
Part 1: How much water do I put in the bottle?
I want to dose 1 ml per gallon of tank volume.
I have 700 gallons worth of tanks to fertilize.
If I mix up 2.1 liters of fertilizer and dose 3 days a week that is exactly right.
(3 days per week x 700 ml = 2100 ml)
So, I use old fertilizer bottles that are labeled 2 liters, but actually hold a bit more.
Part 2: How much fertilizer do I put in the bottle?
I started with EI, so I put enough of each fert in the bottle for 700 gallons worth of aquariums for 1 week.
I made up 2 bottles, 1 for macros, 1 for micros.
I use tap water. (My tap water is pretty good, no toxins except chloramine)
I keep it at room temperature.
The bottles last for 1 week, unless I decide to dose more.
I am currently dosing a modified EI:
Much less nitrogen. (KNO3)
P as per EI. (KH2PO4)
Much more K2SO4. (Since I am using so little KNO3 that is not a significant amount of K, and the plants have shown me that K is the first thing they run out of)
No GH booster. My tap water has about GH 4-5 degrees, and this holds stable enough for me to assume that the plants are not removing the Ca or Mg so fast that I need to add GH Booster. Topping off and water changes are enough.
Micros per EI, (I use CSM+B)
Add extra chelated iron.