Aquarium Fertilisers: All-in-One vs. Separate Nutrient Dosing – Which Is Right for You?

Fertilising your planted aquarium is key to achieving healthy, vibrant plant growth and keeping algae at bay. But with so many fertiliser options on the market, one common question aquascapers ask is: Should I use an all-in-one fertiliser, or dose nutrients separately?

In this post, we’ll break down both methods, explore the pros and cons, and help you choose the best approach based on your tank’s needs and your aquascaping goals.

Why Do Aquarium Plants Need Fertiliser?

Just like garden plants, aquatic plants require a steady supply of nutrients to grow, photosynthesise, and thrive. These nutrients fall into two main categories:

• Macronutrients – Nitrogen (N), Phosphorus (P), Potassium (K)

• Micronutrients/Trace elements – Iron (Fe), Magnesium (Mg), Manganese (Mn), Zinc (Zn), there are more elements including things like Boron, Cobalt, Nickel etc. but these are in even smaller values and generally included in most trace element fertilisers such as Seachem's Flourish Trace.

In nature, these nutrients are constantly replenished through decaying organic matter and sediment. But in a closed aquarium system, especially high-tech setups with strong lighting and CO₂ injection, nutrients are quickly used up and must be replenished regularly through fertilisation.

What Are All-in-One Fertilisers?

All-in-one (AIO) fertilisers combine all essential macro and micronutrients into a single bottle, offering a convenient, balanced dosing method for plant growth. They're ideal for beginners, low-tech tanks, or anyone looking for a simple dosing routine.

Benefits of All-in-One Fertilisers:

• Super convenient – One bottle, one dose, minimal hassle.

• Great for low to medium light tanks or hybrid dosing routine s (AIO + Separate)

• Reduces the risk of overdosing individual nutrients.

• Widely available and often backed by reputable brands (e.g., APT Complete, Tropica Specialised, Seachem Flourish Comprehensive).

Drawbacks:

• Less flexibility – You can’t adjust individual nutrient levels.

• Some formulas may exclude nitrate or phosphate to avoid algae risk, which can actually lead to deficiencies in plant-heavy tanks.

• May not supply enough nutrients for high-tech, fast-growing aquascapes.

What Is Separate Nutrient Dosing?

Separate dosing involves using individual bottles for each group of nutrients—typically:

• Nitrogen (N)

• Phosphorus (P)

• Potassium (K)

• Micronutrients (Trace Elements)

• Iron (Fe)

This method allows for fine-tuned control and is popular among advanced hobbyists or those running high-demand setups.

Benefits of Separate Dosing:

• Precision – Tailor nutrient levels based on your plants' specific needs, or purposely limit certain nutrients such as nitrate to enhance reds ( see this blog post for information on nitrate limitation)

• Ideal for high-light, CO₂-injected tanks with rapid plant growth.

• Easier to spot and correct deficiencies or imbalances.

• Compatible with methods like Estimative Index (EI) 

Drawbacks:

• More complex – Requires multiple products, calculations, and regular testing.

• Not as beginner-friendly.

• Overdosing risk if not carefully managed.

All-in-One vs. Separate Dosing: Which Should You Use?

A Hybrid Approach

Many aquascapers find success using a hybrid approach—starting with an all-in-one fertiliser for convenience, then adding individual nutrients (like potassium, iron or nitrate) as plant demands increase or deficiencies become noticeable.

This method offers the best of both worlds: ease of use with the flexibility to respond to specific plant needs.

Why Root Tabs Shouldn't be Overlooked

Root tabs deliver nutrients right into the substrate, making them perfect for root-heavy plants like:

• Cryptocorynes

• Echinodorus (Amazon swords)

• Vallisneria

• Stem plants that establish deep roots

These plants absorb most of their nutrients through their roots, so root tabs ensure they get what they need even if the water column is low in nutrients.

Boosts Growth in Nutrient-Depleted Substrates

Over time, aquasoil can run out of nutrients. Root tabs recharge the substrate without needing to replace it, keeping plants healthy long-term.

Helps in Inert or Low-Nutrient Substrates

In gravel, sand, or aquasoils with low nutrient content (like ADA Africana or Malaya), root tabs are a must-have to support plant growth. They compensate for what's missing in the substrate.

 Targets Plants Without Overdosing the Water

Unlike liquid fertilisers, root tabs localise nutrients to the root zone. This:

• Reduces the risk of algae caused by excess nutrients in the water

• Is great in shrimp tanks or low-tech setups where you want precise control

Cost-Effective and Low Maintenance

Root tabs are:

• Easy to use — just push into the substrate every few months depending on the plants and growth rate 

• Budget-friendly — long-lasting and simple to apply

Final Thoughts

There’s no one-size-fits-all answer when it comes to aquarium fertilisation. All-in-one fertilisers are perfect for those seeking simplicity and low-maintenance care, while separate nutrient dosing gives you full control—ideal for experienced hobbyists or demanding aquascapes.

Whichever route you choose, the most important thing is consistency and balance. Healthy, well-fed plants grow vigorously, resist algae, and bring your aquascape to life.

Frequently Asked Questions About Aquarium Fertilisers

Do I really need to use fertiliser in a planted tank?

Yes. Even if you have nutrient-rich substrate, over time the water column and substrate nutrients get depleted. Fertiliser replenishes essential nutrients to keep plants healthy, vibrant, and algae-free.

What nutrients do aquarium plants need?

Aquarium plants need both macronutrients (Nitrogen, Phosphorus, Potassium) and micronutrients (Iron, Magnesium, Zinc, etc.). All are vital for growth, photosynthesis, and overall plant health.

How often should I dose fertiliser?

It depends on your tank setup.

• Low-tech tanks: 1–2 times per week is often enough or after each weekly water change

• High-tech/CO₂ tanks: Daily or every other day dosing is common.
  Follow the dosing instructions on your fertiliser and monitor plant response.

What happens if I overdose fertiliser? Will it cause algae?

Excess nutrients alone do not generally cause algae, imbalances between light, CO₂, and nutrients do. It’s more common for algae to appear from not fertilising than fertilising. Still, follow recommended dosages and adjust based on plant growth and tank conditions.

Can I use root tabs instead of liquid fertiliser?

Yes, especially for root-feeding plants like Cryptocoryne, Echinodorus, or carpeting plants. Root tabs supplement nutrients in the substrate, while liquid fertilisers feed plants through the water column.

What’s the difference between macro and micronutrients?

• Macronutrients (N, P, K): Needed in large amounts for leaf, root, and stem development.

• Micronutrients (Fe, Mg, Mn, etc.): Needed in smaller amounts but still crucial for enzymatic and metabolic functions including photosynthesis. 

What are signs of nutrient deficiency in aquarium plants?

• Yellowing leaves (chlorosis): Often iron or nitrogen deficiency.

• Stunted growth or pale new leaves: Possible nitrogen or potassium deficiency.

• Pinholes or melting leaves: Potassium or micronutrient imbalance.
  Diagnosing deficiencies helps you adjust your dosing accurately.

Is CO₂ injection required when dosing fertiliser?

Not always. Low-tech tanks can still benefit from fertilisers without CO₂, but plant growth will be slower. In high-tech setups, adding CO₂ significantly boosts nutrient uptake and plant growth, making proper fertilisation even more important.