Depending on your lighting and whether you're adding co2 and the type of plants you want, there are several ways you could do that. What I would do is look through here and read about low tech setups and high tech setups, both can result in beautiful tanks, low tech just grows much slower. I have a high tech tank and use the "Estimative Index" or EI method of fertilization which I believe is the easiest method, you basically add more nutrients than your plants need which allows them to grow very fast and out compete the algae for food, but I also have moderate lighting and a bottle of co2 injecting into the tank. As for the types of ferts, no matter what method you end up using do diy, you can get potassium nitrate, pure KNO3, at home depot as "spectra brand stump remover" for like 12 bucks, and monopotassium phosphate, KH2PO4, online from hydroponics websites or other planted tank sites for like 15 bucks for 3 lbs, these two ferts supply N, P, and K in sufficient quantities for all but the largest of tanks and are way more than you'll ever need, I took a few teaspoons of them and made solutions and haven't gone back to remake a solution for months I'll probably lose the ferts before I run out...okay I rambled a little, but do some research on which tank type you want and we can point you in the right direction
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