Best Aquarium Plant Fertilizer

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Do you have a planted aquarium that doesn’t look quite as verdant as you’d like? Or are you thinking about upgrading from a fishbowl to a planted aquarium? If so, you’re probably in the market for the best aquarium plant fertilizer to kick start your plants’ growth and health.

In this article I’ll review five of the best aquarium plant fertilizers:

Looking at all the potions and pills available can be confusing, especially with the ‘sciency’ language written all over them. If you need to know more to make an informed choice keep reading and I’ll get into the nitty-gritty details after the reviews. 

The Best Aquarium Plant Fertilizer: My Top 5 Picks

I’ve gathered up 5 of the best fertilizers for your aquarium plants below. All of these have a proven track record and are widely available.

Seachem Flourish Freshwater Plant Supplement

The first on my list is a stalwart of hobbyists and serious aquaculturists across the globe. The Seachem brand has a great reputation and, in my opinion, it’s well deserved. A quick look at the bottle shows the full range of macro and micronutrients your tank and plants need. 

The bottle says “shake well before use” and never has a truer word been said. The solution will separate into layers if left on a shelf. You really do need to give the bottle a good, hard shake about before dispensing otherwise the dose will be wildly inaccurate. 

The 500-milliliter bottle is a decent size and 5-milliliter capful will fertilize 80 liters of tank water. One bottle is going to go a long way. Seachem’s Flourish also has dissolved copper (Cu) but at low enough levels to be safe for shrimp and other crustacea. 

Pros 

  • Great range of nutrients, ticks all the boxes
  • The price for an all-in-one solution is good
  • Simple and easy to use

Cons

  • If using in a heavily populated tank, the extra nitrogen and phosphorus may be an issue

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NilocG Aquatics Aquarium Fertilizer Shrimp Specific

Another liquid fertilizer with a slight twist, NilocG’s product is specifically tailored for heavily planted tanks that are populated with crustacea. The nutrient list has been tweaked with respect to the balance of both macro and micronutrients, notably copper and nitrogen. 

My favorite feature about this fertilizer is the handy pump dispenser, one squirt for five gallons of water—nothing could be easier. The range of nutrients is the same as Seachem’s offering but with amended amounts. 

Reported results indicate the product works great across the board. Users note no ill effects on fauna and flora that goes from strength to strength. On the downside, this fertilizer’s price sits at around double that of the Seachem fertilizer above and there’s a lot less of it in the bottle. However, you really do get what you pay for.

Pros

  • The dispenser is a great idea
  • Bespoke ingredients ideal for specific tank needs

Cons

  • More expensive than comparable liquid fertilizer brands

>>Check Price on Amazon<<

Seachem Flourish Tabs Growth Supplement

Tabs should be buried in the substrate. If you’re not sure how many to use, just remember that a ten-gallon tank requires six tabs and work it out from there. 

They should be replaced every two to three months (or as needed depending on the tank’s ecosystem). With the 40 tabs in this packet, you won’t have to go fertilizer shopping too often.

I like Seachem’s range; it’s unfussy and the products do exactly the job they’re supposed to do. The nutrient balance is spot on too. Unlike liquid fertilizers, these slow-release tabs help eliminate the possibility of a nitrate spike. 

The pH-balanced tabs won’t upset the tank’s balance or the hardness of the water, which other substrate-based fertilizers may do. 

One of my pet hates is tabs or substrates that start to break down as soon as you place them in the water. Not only does it cloud the water, but it also defeats the point of a slow-release system. There’s no danger of that here, the tabs are firm, compact and easy to handle and situate. 

Pros 

  • Low maintenance fertilizer (use once every two to three months)
  • Good nutrient balance
  • Excellent value for money
  • Firm tabs, don’t break down when handled or placed in the tank

Cons

  • If the nitrogen load becomes too heavy in a well-stocked tank, removal can be wet, fiddly, and messy

>>Check Price on Amazon<<

Aquatic Arts Marimo Moss Ball Food

Aquatic Arts’ fertilizer is a left-field addition to the list because it’s a special, tailored plant food designed for Marimo moss balls, delightful little algae balls that float by day and sink at night. The Japanese know how to create novelty pets, and these guys certainly qualify. 

The moss balls need one drop of this fertilizer every few days (the bottle features a handy drop dispenser). The balls should be fed individually, one drop per ball (although, no more than three if you are feeding directly into their water) and rolled around in your hand to disperse the food across each ball’s surface.

The nutrient balance has been altered to cater specifically for Marimo moss balls. One of the only products out there to make this boast!

Along with regular water changes, this is the only care your moss balls should ever need, so this is a great all-in-one cure-all. The only downside, if there is one, is that if your moss balls are in a tank with other fauna, they need no feeding, making fertilizer redundant. 

Pros 

  • An all-in-one solution
  • Simple and easy to use
  • Tailored to the mosses metabolic requirements

Cons

  • Technically, you could use any fertilizer for your Marimos at less cost

>>Check Price on Amazon<<

API LEAF ZONE

API’s LEAF ZONE is a completely different animal to the previous offerings we’ve looked at. Where the others had a full range of micro or macronutrients, LEAF ZONE  contains potassium and iron only. Both are needed for healthy plant growth so this will give your plants a boost.

The fertilizer can be put to good use in a well-established, mature tank that’s stocked with fish. Together, the plants and the bioload from the fish create a delicately balanced nutrient cycle. API’s product acts as a pick-me-up, without overloading the flora or fauna with nutrient spikes. 

Pros

  • Fantastic value for money
  • Won’t overload a mature, well-stocked tank
  • No risk of nitrate spikes

Cons

  • Limited nutrients with only two in the bottle. Not suited to fledgling tanks or plants

>>Check Price on Amazon<<

So Which is the best?

Looking at the five products it’s clear there’s one winner: Seachem Flourish.

While there are some good options here, and all are winners in their own right, Flourish has the edge with its great range of nutrients. It is also well-balanced and crustacean safe, a downfall of some other fertilizers. Flourish is easy to use and the dispenser was a great addition. 

For the price, the results, and the tank plants’ growth and health after a week of using Flourish, it can’t be beaten.

What to Look for in an Aquarium Plant Fertilizer:

Still not sure which is best for you? There are a variety of considerations to take into account for your specific application. There are also some things you need to understand about your plants as well as fertilizers in general. Read on to get the important facts.

Things you should look for and consider include:

  • A clear breakdown of the fertilizer’s contents detailed on the bottle
  • Price
  • Suitability for your tank, tank inhabitants, and water type
  • Ability to tailor the nutrients to your tank’s specific needs 
  • Choose the best option for your tank between liquid and substrate fertilizers
  • Consider how often the fertilizer should be used. Daily, weekly or monthly and does this fit with your schedule? 

From the start, I’ll be clear that not all planted tanks are equal. In fact, it’s fair to say that all planted tanks are different. When choosing a new fertilizer regime, you have to take into account many factors from lighting quality and hours (the photoperiod) to CO2 levels in your tank. 

The planting density and the type of plants you keep obviously have a huge impact on the fertilizer system you end up going with. Fast-growing aquarium plants have higher nutrient requirements than low light aquarium plants for instance. The number and types of fish will also impact on your choice, we have to factor in their bioload too. 

We also have to consider the size of your tank because believe me, size really does matter. 

Lastly, the substrate you plan to use in your aquarium will make a difference. Is it inert (no nutrients) or is it an enriched complete aquarium plant substrate? If its the latter you may not need to add fertilizer right away as the substrate will provide the needed nutrients. Before you choose a substrate check out my article Best Substrate For a Planted Aquarium to learn more.

With these considerations at the front and center of your purchasing decisions, let’s look at some of the key things you should know about aquarium plant fertilizers. 

The Types of Aquarium Plant Fertilizers: Root and Leaf Feeders

There are two main types of fertilizer on the market because there are two ways that your aquarium plants feed. 

The plants you have will either take in nutrients via their root system as normal garden plants do, or they will intake nutrients via their stem and leaves (known as foliar feeding). Some plants do a little of both but we’ll bypass detailed info on those here as they feed well from both systems. 

Common root feeders include:

  • Sagittaria
  • Amazon sword
  • Dwarf hair grass
  • Cryptocoryne
  • Vallisneria

And some leaf/stem feeders you might be familiar with include:

  • Duckweed
  • Red Root Floater
  • Water Lettuce
  • Hornwort 

For the first group (root feeders), you’ll need a liquid fertilizer. It’s simple to feed your plants with this, just adding drops or dilution to your tank is sufficient. The second group of plants (leaf/stem feeders), requires a substrate based fertilizer. 

The latter comes in various forms including underwater ‘soil’ for your plants to grow in or tabs of nutrients that you bury in the inert substrate at the bottom of your tank. 

What’s in Aquarium Plant Fertilizer?

Regardless of whether you buy fertilizer from root or foliar feeders, there are two types or classes of nutrients in that fertilizer: micro and macronutrients. The micronutrients are those used in relatively small quantities and the macronutrients are in larger quantities. 

Macronutrients: 

  • Nitrogen (N)
  • Phosphorus (P)
  • Potassium (K)

Micronutrients:

  • Iron (Fe)
  • Chlorine (Cl)
  • Cobolt (Co)
  • Boron (B)
  • Molybdenum (Mb)
  • Nickel (Ni)
  • Manganese (Mn)

A deficiency in any of these key nutrients can cause problems. For a quick overview on identifying and treating nutrient deficiencies check out this video.

Using Micro and Macronutrients

The key macronutrients in aquarium plant fertilizers are listed as that fertilizer’s NPK value. NPK is a guide to the relative amounts of three of the most important macronutrients present—nitrogen, phosphorus, and potassium. 

Pay careful attention to these three values as they are absolutely crucial to the health of your flora and fauna. If you get it wrong, it can go badly, badly wrong. The results range from an annoying and unsightly algal bloom to the death and destruction of both your fish and plants. 

You will remember earlier that I said no two tanks were the same. Well, this is where understanding that really matters. 

The amount of NPK your plants need depends on how heavily planted your tank is and your lighting and CO2 systems. It also depends on how densely stocked with fish you keep the tank. Their bioload (poop and so on) contains lots of nitrogen and phosphorus, so adding an NPK heavy fertilizer can cause problems. 

If you have a plant-heavy tank with only a few shrimp, for example, then NPK is the way to go. 

You will want to look for a fertilizer with a good range of micronutrients too. It’s important to get the balance right as algae can be the least of your worries. Note that the addition of some liquid fertilizers may temporary cloudiness in the water. But don’t be alarmed, this should soon pass. 

If you are adding substrate (or tablet fertilizer) be aware these can leach ammonia into the tank initially. If you already have a heavy bioload, this can tip the balance and your plants and animals will be in dangerous waters, literally.  

Keeping an eye on the tank’s pH, water hardness, and carrying out regular water-quality testing is a must.

Final Thoughts

Hopefully, this article has educated you as to what you need in fertilizer as well as some top products. Just remember that there is a lot more to growing aquarium plants than fertilization. Light, water quality, temperature and substrate all play a role.

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