I have a 2.5 and use the same liquid co2. 1/10 = x/2.5.... x = .25ml which is 5 drops per day. But the margin for error is smaller in small tanks. I make sure I have enough fertilizer so that I can adjust light and co2 to get the growth I want then I cut fertilizer, light and co2 down a bit so that the tank is in a somewhat of a limited resource state so growth is slower. I use 2 drops per day on my medium planted tank of co2. But I use co2 because I dose, dosing without proper nutrients for your plants makes your tank very susceptible to algae because the plants cannot grow so the co2 you are adding is going to aid the growth of algae instead of the plants.
Continuing on about nutrients/fertilizer... you need macro and micronutrients for your plants to grow. You can give your plants plenty of Co2 but if the tank is deficient in one or more macronutrients the plants will not use the carbon from co2 or any other macronutrient (nitrogen, potassium, phosphorus) to the degree they normally would either.
This is because a plants growth is determined by the limiting (deficient) nutrient [Liebig's law of the minimum]. So, if you are for example, deficient in potassium, which isn't found in plant or animal waste or in tap water plant growth will be difficult. Because of this lack of growth, your plants will also not be consuming the other macros like nitrogen, phosphorus, and carbon. But if you give them enough potassium they will then begin to grow and absorb and utilize the other macronutrients again. To side track... this can create a problem of adding co2 and getting algae and then believing you are adding too much co2 when in reality your plants are missing a macronutrient and aren't utilizing the co2 that's available which is going to algae is instead. But correcting the deficiency allows the plants to grow, take up co2 and out compete the algae, eliminating it.
I use separate macronutrients and flourish comprehensive and flourish Iron for micronutrients but you can buy all in one macro+micro nutrients but for a smaller tank I just think more control over what you are adding is necessary in a smaller tank due to that small margin of error and the fact that any tank with unbalanced nutrients is susceptible to algae that will take advantage the second they can.
I dose 2 drops co2, 5 drops iron a day (recommended dose), flourish comprehensive 4 drops once a week (recommended), potassium 4 drops a week (recommended). As far as nitrogen and phosphorus....I dose Phosphorus based what my phosphate test kit shows my current level is and my nitrate(nitrogen) reading because I know the ratio the two should be to each other. If nitrate test shows 0ppm I add flourish nitrogen to get to 5-10ppm. ratio between nitrogen and phosphate should be 10:1. I don't have to do the phosphate test every time I dose now as after I did it for a few months I became familiar with how much phosphates my plants take up. so I add 2 drops a week of phosphate. The general ratio for macronutrients is something like this: 1P:10N:20K (phosphorus, nitrogen, potassium)
Last edited by nothreat33; 08-06-2019 at 12:59 PM.
Reason: i keep wanting to add mroe