Quick answer: DIY dosing uses five dry salts: KNO3, KH2PO4, K2SO4, Epsom salt and a chelated trace mix. Indian hobbyists buy them from lab-chemical suppliers, hydroponics sellers or marketplaces, avoiding fertiliser-grade salts with anti-caking agents. Start with conservative weekly doses per 100 litres, pair EI with big water changes, and accept that for one small tank a bottled fertiliser is often the sensible choice.
What the dry salts actually are
DIY dosing means buying a few water-soluble salts and adding them to the tank yourself instead of pouring from a bottle. Five components cover nearly everything a planted aquarium needs from the water column, and each one has a specific job.
- Potassium nitrate (KNO3) is the nitrogen source, and it carries a useful amount of potassium along with it.
- Monopotassium phosphate (KH2PO4) supplies phosphate, plus a little more potassium. The quantities involved are tiny, which is exactly why people overdose it.
- Potassium sulphate (K2SO4) tops up potassium on its own, for when nitrate and phosphate are already where you want them.
- Magnesium sulphate (MgSO4.7H2O, plain Epsom salt) supplies magnesium. It matters most in soft or RO-heavy water; a lot of Indian tap water is hard enough to cover magnesium already.
- A chelated trace mix delivers iron, manganese, zinc, boron, copper and molybdenum in one powder. Chelation matters: EDTA iron falls apart quickly above pH 7, and plenty of Indian tap water sits there, so DTPA or a blended chelate holds up better.
Note what is missing. None of these salts is a carbon source, none fixes poor light, and none compensates for a tank that is simply too new. Dry salts replace the bottle, not the rest of your setup.
Where Indian hobbyists actually source them
There are three realistic routes in India. Local chemical and laboratory suppliers are the most reliable: most cities with any industry have a lab-chemical shop, and Surat, Ahmedabad, Mumbai, Delhi, Bengaluru and Chennai all have several. Ask for laboratory grade or analytical reagent (AR/LR) grade and expect to buy 500 g or 1 kg at a time.
Hydroponics suppliers are the second route, and often the cheapest per kilo. Their potassium nitrate and monopotassium phosphate are usually sold as water-soluble fertiliser and are generally fine, but you need to read the label rather than the product title. The third route is the online marketplaces, where the listings are a mix of genuine lab chemicals, hydroponic salts and repackaged unknowns. Aquarium-specific sellers on Indian marketplaces do stock pre-weighed DIY kits, which cost more per gram but remove the guesswork.
The purity caution, which is not optional
Never use agricultural or garden fertiliser-grade salts with anti-caking agents, coatings or unlisted additives. Anti-caking compounds, urea blends, ammoniacal nitrogen and trace contaminants such as copper-heavy mixes can be harmful to shrimp and fish, and you have no way to test for them at home. A bag labelled only NPK 13:0:45 with no ingredient breakdown is not worth the saving.
Two practical checks: the salt should dissolve completely in a glass of warm water with no cloudiness or floating film, and the seller should be able to tell you the grade. If either fails, do not put it in a tank with livestock.
Stock solution or dry dosing?
Dry dosing means measuring the powder and dropping it straight into the tank, usually into a filter outflow so it disperses. It is faster and there is nothing to go off, but home measuring spoons are wildly inconsistent, and at the quantities phosphate needs, a spoon that is 30% out is a real error.
A stock solution means dissolving a weighed amount of salt into a known volume of water and dosing millilitres with a syringe. It is far more repeatable and much kinder to small tanks. Keep macros and traces in separate bottles, because concentrated phosphate and iron mixed together will precipitate into a rusty sludge that your plants cannot use.
Stock solutions are unsterile water sitting in a warm room, so make small batches that you will finish in three to four weeks, keep them out of sunlight, and discard anything that goes cloudy or stringy. A cheap digital jewellery scale reading to 0.01 g makes all of this dramatically easier than any spoon.
Conservative starting doses per 100 litres
Treat every figure below as a starting point to test and adjust, not a prescription. Tanks differ in plant mass, light, livestock load and tap water, and the honest answer is that your tank will tell you more than any table can. Start at the low end, hold it for three to four weeks, and change one thing at a time.
For a low-tech tank without CO2, a reasonable weekly total per 100 litres is roughly 0.5 to 1.5 g of KNO3, 0.1 to 0.3 g of KH2PO4, and 0.5 to 1.5 g of K2SO4, split across two or three doses rather than dumped in at once. Traces go in on the days you are not dosing macros, at whatever rate the trace mix specifies, starting at half that. Magnesium only if your water is soft or you see the symptoms described below.
Estimative Index dosing for a pressurised CO2 tank runs considerably richer, because fast growth genuinely consumes more. Per 100 litres, EI-style dosing typically lands around 1.5 to 2.5 g of KNO3 and 0.3 to 0.5 g of KH2PO4 three times a week, with traces on the alternate days and a large weekly water change to reset. Running EI numbers in a low-tech tank without CO2 is one of the more common ways Indian hobbyists end up with an algae problem.
Reading the plants instead of guessing
Deficiency symptoms overlap, so treat these as hints that point you somewhere rather than diagnoses. Older leaves fading to a uniform pale yellow, with growth slowing across the tank, usually points at nitrogen. Pinholes and small necrotic spots on older leaves, often with a yellow halo, are the classic potassium signal.
Phosphate shortage is subtler: stunted new growth, darker or slightly purplish older leaves, and in some tanks a rash of green spot algae on the glass and on old Anubias leaves. Iron shows as yellowing between the veins on new growth, with the veins staying green; the same interveinal yellowing on old leaves points at magnesium instead. Check your light and CO2 before adding more of anything, because poor growth from weak lighting looks a lot like a deficiency and no amount of fertiliser will fix it.
Water changes and why EI needs them
EI deliberately doses more than the plants can use so that nothing ever runs short, and it relies on a 40 to 50% weekly water change to stop that surplus accumulating. Skip the water change and you are no longer doing EI; you are just building up nutrients in a closed box, which is an unpleasant place for shrimp and a pleasant one for algae.
Low-tech tanks are gentler. A 25 to 30% weekly change, with the dose going in straight afterwards, keeps things stable and matches the rhythm we recommend elsewhere on this site. If you cannot commit to weekly water changes, dose lean and stay lean rather than chasing lush growth you have no way to reset.
When DIY is genuinely cheaper, and when it is not
The economics are simple. Dry salts are sold in 500 g and 1 kg lots, and a kilo of potassium nitrate will outlast several years of dosing on a single 100 litre tank. If you run multiple tanks, a big display, or a CO2 setup on EI, the per-litre cost of DIY is a fraction of bottled fertiliser and the savings are real.
For one modest low-tech tank, the maths is much less flattering. You are buying four or five kilos of chemicals, a scale, syringes and bottles to replace something that might cost a few hundred rupees a year to dose from a bottle, and most of it will expire in the cupboard before you use it. Sourcing, shipping and the minimum order quantities are the real cost, not the salts.
If you would rather skip all of it, our own Green Plus + Trace Fertilizer is the no-effort option: the two-part 100 ml + 100 ml set is Rs 250 and the 250 ml + 250 ml set is Rs 410, dosed after the weekly water change. It is not cheaper per litre of tank water than DIY at scale, and we would not pretend otherwise, but it involves no weighing and no chemical shopping.
Safety and storage
Label every container with the chemical name, the concentration if it is a stock solution, and the date you made it. Unlabelled white powders in kitchen jars are how people dose potassium nitrate thinking it is Epsom salt.
Keep everything well away from children, pets and food, in a separate cupboard from anything edible, and never in a drink bottle. These are not food-safe substances; potassium nitrate in particular is a strong oxidiser and should be kept dry and away from heat and anything combustible. Wear gloves if you are handling powders often, avoid breathing the dust, and mix in a ventilated spot. Mixing your own fertiliser is a normal hobby activity, but it is not risk-free, and it deserves the same care as any other chemical you keep at home.
Plants in this guide
![Green Plus + Trace Fertilizer [ 250ML + 250ML ]](https://anubias.in/wp-content/uploads/2026/04/1000647632-513x654.jpg)
![Green Plus + Trace Fertilizer [ 250ML + 250ML ]](https://anubias.in/wp-content/uploads/2026/04/1000647617-513x729.jpg)
₹ 410 ₹ 580
₹ 250 ₹ 410
Price range: ₹ 90 through ₹ 250
₹ 175 ₹ 320
Frequently asked questions
Where can I buy KNO3 and KH2PO4 in India?
Local laboratory and chemical suppliers are the most dependable source in most Indian cities, sold as LR or AR grade in 500 g or 1 kg lots. Hydroponics suppliers are usually cheaper per kilo and generally fine if the label lists the actual compound. Online marketplaces work too, including aquarium sellers offering pre-weighed DIY kits, but check the grade before buying.
Can I use garden or agricultural fertiliser instead?
No, not unless the full ingredient list is printed and the salt is a single named compound. Agricultural blends often contain anti-caking agents, urea, ammoniacal nitrogen or unlisted trace contaminants, and you cannot test for any of that at home. With shrimp or fish in the tank, the saving is not worth the risk.
Is DIY dosing actually cheaper than bottled fertiliser?
It is, clearly, if you run several tanks or a CO2 tank on EI, because a kilo of each salt lasts years. For a single low-tech tank the minimum order quantities, a 0.01 g scale, syringes and bottles usually outweigh what you would spend on a bottle, and most of the powder expires unused in the cupboard.
How much KNO3 should I dose in a 100 litre low-tech tank?
Start low: roughly 0.5 to 1.5 g of KNO3 per 100 litres per week, split across two or three doses, then hold that for three to four weeks and watch the plants. Adjust one nutrient at a time. These are starting ranges, not prescriptions, because plant mass, light and tap water differ in every tank.
Do I have to do water changes if I dose dry salts?
For EI dosing, yes, absolutely. EI deliberately supplies more than the plants use and relies on a 40 to 50% weekly water change to clear the surplus. A lean low-tech schedule is more forgiving, but a 25 to 30% weekly change with the dose going in straight afterwards is still the routine we would recommend.
Or skip the mixing
If you would rather not weigh salts, the ready-mixed bottles are in the fertiliser category.
