There is no best aquarium fertiliser, only the right one for the tank in front of you. The choice comes down to how much nutrient your plants can actually use, and that is set by light, CO2 and plant mass. This guide walks through the four situations and which AquaLabs fertiliser suits each.
Start with demand, not with the bottle
Every fertiliser question is really the same question: how much can your plants use?
Dose less than that and growth stalls. Dose more and the surplus accumulates in the water, because there is nothing there to take it up. You are paying for nutrient that sits in the tank until the next water change removes it.
So the useful thing to work out is not which bottle is best. It is how much demand your aquarium actually has.
What sets demand
Light drives photosynthesis, and photosynthesis is what consumes nutrients. A high output light over a shallow tank creates far more demand than a modest light over a deep one.
CO2 is the single largest nutrient input a plant needs, and in most aquariums it is the limiting one. Injecting CO2 typically multiplies growth rate several times over, and nutrient demand rises with it. This is the biggest single fork in the road.
Plant mass matters more than tank size. Twenty stems of rotala consume vastly more than three anubias on a piece of wood. Fast growing stems are hungry, slow growing rhizome plants are not.
All three have to line up. High light without CO2 does not give you fast growth, it gives you algae. Heavy dosing without the light and CO2 to use it gives you nothing at all.
Then subtract what your fish already provide. In a heavily stocked, lightly planted aquarium, fish waste can supply most or all of the nitrogen and phosphate the plants can use. What those plants are usually short of is potassium, magnesium and iron, which fish waste does not supply.
The four situations
Four formulations because there are four situations. Find your tank on the chart rather than working up a ladder.
Easy Grow Lite
A community tank with a decent fish load and a modest number of plants. Anubias, java fern, crypts, a few swords. The fish are already producing nitrate and phosphate faster than that plant mass can use it.
@tanknut has a stunning planted discus display. The slow growing plants would benefit from AquaLabs Easy Grow Lite to prevent buildup of nitrate and phosphate.
Easy Grow
The most common planted aquarium. Reasonable plant mass, no CO2 injection, a normal fish load. Growth is steady rather than fast, and demand is real but moderate.
Complete nutrition including nitrate and phosphate, at a level a low tech tank can use.
@horizonaquaticsuk low tech aquarium. Perfectly suited to AquaLabs Easy Grow.
Lean Grow
A scape built around wood and stone, with plants used deliberately rather than filling the tank. Often with red species where colour matters more than growth rate. You want healthy plants that stay in proportion to the layout rather than growing over it.
Lean Grow is lean on nitrate for a CO2 injected aquarium. A tank with CO2 could take considerably more, and holding it back is what deepens colour in red species and slows growth so there is less trimming.
@gloriaciriello_aquascaper on Instagram has a tank perfectly suited for Lean Grow
Max Grow
Stem plants, carpets, a full tank of fast growers under strong light with CO2. Demand here is genuinely high, and limiting nutrients means stunted tips and pale new growth.
Non limiting nutrition so growth is never held back by what is in the water.
@fantoni_aquarismo dutch style aquarium is perfect for Max Grow
These are not a good, better, best ladder
Worth saying plainly, because the names invite it. Max Grow is not the premium version of Easy Grow. It is the right formulation for a tank with high demand and the wrong one for a tank without it.
Dosing Max Grow into a low tech tank with six anubias will not make them grow faster. Growth there is limited by carbon and light, not by fertiliser, so the extra nitrate and phosphate has nowhere to go and will likely cause algae.
Equally, running Easy Grow Lite in a densely planted CO2 tank will starve it. No added nitrate or phosphate is correct in a fish heavy, plant light tank and completely wrong in a plant heavy one.
What should my nitrate reading be?
This is worth being specific about, because a lot of advice avoids giving a number at all.
Around 10 ppm suits most planted aquariums. It is comfortably above deficiency, well within safe limits for fish and shrimp, and gives you a margin if you miss a dose. If you want one number to aim at, that is it.
0 to 3 ppm brings out the deepest reds. Restricting nitrate in the water column is what pushes red pigmentation in species like rotala and ludwigia. But there is an important condition attached: this only works when a rich aquasoil is supplying nitrogen through the roots. Run 0 to 3 ppm over inert gravel and you are not creating colour, you are starving the tank and inviting algae.
Testing is worth doing rather than dosing blind. It tells you whether your dose is landing where you intend, and whether your plants are consuming it faster or slower than you expected.
Root tabs are a different question
Enrich Root Tabs are not an alternative to the four above. They answer a different question: where the nutrient is delivered, rather than how much.
Liquid fertiliser feeds through the water column and leaves. Root tabs feed the substrate. Heavy root feeders such as swords, crypts and larger stem plants take a substantial share of their nutrition through roots and do noticeably better with a substrate source available.
Add root tabs alongside any liquid fertiliser if you have heavy root feeders, an inert substrate such as sand or gravel, or aquasoil more than a year old that has exhausted its nutrients.
They are also what makes lean water column dosing possible in a tank without fresh aquasoil, since the nitrogen arrives at the roots instead.
If your tank does not fit neatly
Most do not, and the answer is usually to dose for the demand you have rather than the tank you intend to build.
- Low tech now, CO2 later? Start with Easy Grow and move up when the CO2 goes on, not before.
- Newly planted CO2 tank? Plant mass is low at the start, so demand is lower than it will be in two months. Start conservatively and increase as the tank fills in.
- Fresh aquasoil? The soil is releasing its own nitrogen and will do for weeks. Hold off on heavy nitrate dosing until it settles, and see how to dark start an aquarium.
- Shrimp tank? All AquaLabs liquid fertilisers are suitable. A lightly planted shrimp tank is usually an Easy Grow Lite situation, since shrimp bioload and food supply nitrogen already.
Water changes
A 30 percent weekly water change is a good baseline for any planted aquarium, and worth doing regardless of which fertiliser you run.
Beyond that, water change frequency is driven by your fish load rather than your fertiliser, with one exception. Max Grow adds considerably more nitrate per dose, so a densely planted CO2 tank running it benefits from around 50 percent weekly to keep levels in range.
Easy Grow Lite adds no nitrate at all, so it has no bearing on how often you need to change water. Your stocking level decides that.
Switching fertilisers
Changing fertiliser can cause a temporary wobble, particularly moving from something very lean to something richer. Plants adjust to what is consistently available, and a sudden change can trigger a short period of instability.
Introduce the new fertiliser over about two weeks rather than all at once. Dose part of the new alongside part of the old, then shift the balance gradually. Consistency matters more than precision.
Common mistakes
Worth avoiding
- Choosing by tank size. Volume affects how much you dose, not which formulation you need.
- Assuming more is better. Surplus nutrient is not stored by plants for later. It sits in the water until you remove it.
- Running lean without aquasoil. Low water column nitrate only produces colour when the substrate is supplying nitrogen. Over gravel it produces deficiency.
- Dosing two complete fertilisers together. Each is complete on its own, so running two doubles some nutrients and unbalances the ratios. Root tabs are the exception.
- Fixing a fertiliser problem that is actually a CO2 problem. In a CO2 injected tank, most symptoms that look like deficiency turn out to be carbon, flow or light related. Rule those out first.
- Changing several things at once. If you adjust fertiliser, light and CO2 in the same week, you will not know which one caused the result.
The short version
- Work out your demand: light, CO2 and plant mass together
- Count your fish, because they already supply nitrogen and phosphate
- Easy Grow Lite: no CO2, lots of fish, few plants
- Easy Grow: no CO2, reasonably planted
- Lean Grow: CO2, hardscape led, colour and control
- Max Grow: CO2, densely planted, maximum growth
- Enrich Root Tabs: alongside any of them, for root feeders and inert substrates
- Aim for around 10 ppm nitrate in most tanks, or 0 to 3 ppm for reds if aquasoil is feeding the roots
- 30 percent weekly water changes as a baseline, 50 percent on Max Grow
- Switch gradually over two weeks
- Dose for the aquarium you have, not the one you are planning
The right fertiliser is the one that matches what your plants can use. Work that out first and the choice makes itself.