Add aquarium fertilizer two to three times a week for most planted tanks, dosing right after your weekly water change and with the lights on so plants can use the nutrients straight away. Low-tech tanks without CO2 need less once or twice a week is plenty while high-tech CO2 tanks may be dosed daily or every other day. Root tabs are replaced every three to four months. This guide explains exactly when and how often to add liquid fertilizer and root tabs, with a simple weekly schedule you can copy, tailored for planted tanks in India.
Timing matters almost as much as the amount. Dose at the right frequency and your plants get a steady supply; dose erratically and you get nutrient swings that stall growth and invite algae.
How often should you add fertilizer?
Short answer: 2–3 times a week for most tanks; once or twice for low-tech; daily or alternate days for high-tech CO2 tanks.
Plants use nutrients continuously, and a liquid dose is gradually consumed over a few days. Re-dosing two to three times a week keeps levels topped up so plants never run short. The exact frequency depends on how fast your plants grow, which is driven mostly by light and CO2. Slow-growing low-tech tanks need fewer doses; fast-growing high-tech tanks need more.
Dosing frequency by tank conditions
Short answer: Match frequency to your light intensity, CO2 and plant density — the faster your tank grows, the more often it needs feeding. Typical all-in-one labels recommend around 1 ml per 10 litres per dose; always follow your bottle's label.
| Your tank conditions | Photoperiod | Dose frequency | Typical amount per dose |
|---|---|---|---|
| Low light, no CO2, lightly planted | 6–7 hours | 1× per week | ~1 ml per 10 L all-in-one |
| Low–medium light, no CO2, moderately planted | 7–8 hours | 2× per week | ~1 ml per 10 L all-in-one |
| Medium light, liquid carbon, densely planted | 8 hours | 2–3× per week | 1–1.5 ml per 10 L all-in-one |
| High light, pressurized CO2, densely planted | 8–10 hours | Daily or alternate days (macros/micros split) | 1.5–2 ml per 10 L, or EI-style dry dosing |
Two useful rules: if you raise your light intensity or photoperiod, raise your dosing frequency with it, and if your tank is sparsely planted, dose less often than these ranges nutrients that plants cannot absorb only feed algae. High-tech tanks running EI-style schedules should see the EI dosing guide for exact macro and micro quantities.
A simple weekly fertilising schedule
This is a starting template adjust the amounts to your fertilizer’s label and your tank’s response. For how much to add each time, see how to dose aquarium fertilizer.
When in the day should you dose?
Short answer: Dose when the lights come on (or shortly before), so plants can use the nutrients during their active photosynthesis period.
Plants take up nutrients most actively while the lights are on and they are photosynthesising. Dosing at lights-on (or an hour before) gives them a fresh supply for the day. Avoid dosing into a dark tank that will sit unlit for hours, as nutrients are simply waiting unused. If you dose after a water change, do the change earlier in the day and dose as the photoperiod begins.
When to add liquid fertilizer vs root tabs
| Fertilizer | How often | When |
|---|---|---|
| All-in-one liquid (low-tech) | 1–2× / week | At lights-on, after water change |
| All-in-one / macros (high-tech) | 3–4× / week or daily | At lights-on |
| Micros / iron (high-tech) | Alternate days | At lights-on, opposite day to macros |
| Root tabs | Every 3–4 months | Pushed into substrate near root-feeders |
| Liquid carbon | Daily (if used) | At lights-on |
Root tabs such as Sunken Garden Root Tabs release slowly, so they are replaced only every few months a different rhythm to liquid dosing. More on this in root tabs vs liquid fertilizer.
Does frequency change with the seasons?
Yes, in India these matters. In summer, warmer water speeds plant metabolism, so plants often use more nutrients and may need an extra dose per week. In cooler months, growth slows and you can ease back. Watch your plants: faster growth means dose a little more often; slower growth means less. This seasonal awareness keeps your dosing efficient year-round.
Signs you are dosing too often or not often enough
- Not enough: slow growth, pale new leaves (iron), pinholes in older leaves (potassium), increase frequency or dose.
- Too much: algae appearing while plant growth is already healthy, ease back and check light/CO2 balance.
- Just right: steady healthy growth, good colour, minimal algae.
Read the plant signals in signs of nutrient deficiency.
Building a routine you will actually keep
The best dosing schedule is the one you stick to. Pick fixed days (for example, dose every Sunday and Wednesday), tie it to your water-change day, and keep your fertilizer and a syringe near the tank. Consistency beats perfection, a steady, modest routine produces healthier plants than occasional heavy dosing. A reliably-stocked, affordable all-in-one like Sunken Garden Green makes a weekly routine easy to maintain.
Stock your weekly routine
Frequently asked questions
How often should I add fertilizer to my aquarium?
For most tanks, 2–3 times a week. Low-tech tanks need once or twice; high-tech CO2 tanks may need daily or alternate-day dosing.
How much fertilizer should I add per dose?
Typical all-in-one liquids recommend about 1 ml per 10 litres per dose (1–2 ml per 10 L in high-tech tanks). Always follow your bottle's label, and see how to dose aquarium fertilizer for exact amounts.
When should I add liquid fertilizer to my aquarium?
At lights-on (or shortly before), after your weekly water change, so plants can use the nutrients during the photoperiod.
When should I dose fertilizer in a planted tank?
Right after a water change and as the lights come on. Keep to fixed days each week for a steady supply.
Should I dose fertilizer every day?
Only high-tech CO2 tanks usually need daily dosing. Low-tech and most community tanks dose a few times a week.
How often do I replace root tabs?
Every 3–4 months, as they release nutrients slowly into the substrate.
Should I dose before or after a water change?
After do the water change first, then dose into the fresh water.
Can I dose fertilizer with the lights off?
It is better to dose at lights-on so plants can use the nutrients immediately. Dosing into a long dark period is less efficient.
Do low-tech tanks need fertilizer as often?
No, low-tech tanks grow slower and need less, so once or twice a week is usually enough.
What happens if I dose too often?
If plants are already healthy, extra dosing can feed algae. Ease back and check your light and CO2 balance.
What if I forget to dose for a week?
Just resume your normal schedule do not double-dose to compensate. Plants tolerate short gaps.
Does fertiliser frequency change in summer?
Yes, in India’s summer heat plants grow faster and may need an extra weekly dose. Slow down in cooler months.
How do I know if I should dose more often?
If you see deficiency signs (pale new leaves, leaf holes, slow growth) with algae under control, increase frequency or dose.
Can I split my weekly dose into smaller daily doses?
Yes, smaller, more frequent doses give very steady nutrient levels and are popular in high-tech tanks.
Should I dose on water-change day?
Yes, dosing after the water change is ideal, then continue on your other scheduled days.
What is the easiest schedule for a beginner?
Water change and dose every Sunday, dose again every Wednesday, and refresh root tabs every few months. Simple and effective.
Make a routine stick with an affordable all-in-one from the Sunken Garden range or the Aquarium Fertilizer collection. Pair this with how to dose aquarium fertilizer and the complete fertilizer guide.
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