Aquarium Plant Supplements and Whether Extra Additives Are Worth the Money

Walk into any aquarium shop and you’ll be forgiven for thinking you’ve stumbled into a chemistry lab’s marketing department.

Bottles upon bottles of every imaginable supplement promising faster growth, healthier plants, better colours, improved recovery rates and anything else their fancy packaging can dream up.

Iron boosters, potassium supplements, trace element cocktails, bacterial additives and mysterious liquid formulations that probably come with their own astronaut program.

Prices quickly spiral and claims get bolder by the moment. But which aquarium supplements are actually useful for your plants? And which ones are fancy ways of doing what a cheap bottle of fertilizer already does?

The truth is that most planted tanks don’t need nearly as many aquarium supplements as companies want you to think. Plant nutritional needs are simple, and if you know what they are and how to meet them cheaply, you can eliminate a lot of unnecessary additives without missing out on anything.

The key is understanding what nutrients your plants actually need, what’s already available from your tap water and what the real gaps are. That being said, there are definite cases where targeted supplementation can help out your plants and improve growth rates.

Knowing when those cases apply to you and your aquarium will save you money and spare you the frustration of buying expensive bottles that aren’t designed to solve your problem.

Taking Stock Of Your Plants Needs

The first thing you need to understand is that plants don’t magically become less finicky about what they eat when you stick them underwater. While there are important differences in nutrient uptake methods and concentrations, aquatic plants have the same basic nutritional needs as terrestrial ones.

The key difference is where they get those nutrients from. While land plants draw most of their nutrition from the soil around their roots, aquarium plants can derive nutrients from both their roots and leaves.

Aquatic plants absorb nutrients applied to the water column through their leaves as well as their roots. Leaves with thin leaves absorb the majority of nutrients this way. Plants with thick waxy leaves tend to root feed much more efficiently.

Your plants still need Macronutrients: Nitrogen, Potassium, and Phosphorus. Aquarium plants use Nitrogen to produce proteins and aid in chlorophyll production. Without enough Nitrogen your plants will lose their green colour and start to turn pale or yellow. Phosphorus plays many roles in cell energy transfer and root development. Potassium affects overall plant growth by regulating its rate of water uptake and the activity of many important enzymes.

Your plants also need plenty of Micronutrients: Iron, Magnesium and several trace elements. Iron helps your plants produce chlorophyll and is often blamed when aquarium plants lose their green hue and start to turn yellow. However, with iron deficiency plants your leaves will typically yellow between the veins while the veins themselves will remain green. Magnesium is a key component of chlorophyll and is vital to your plants’ ability to photosynthesize. Trace elements like manganese, zinc and boron help support numerous enzymes and metabolic reactions.

The important takeaway from all of this is that your plants need all of these things. Supplementing your aquarium with extra iron isn’t going to do you much good if your aquarium is actually Nitrogen or Potassium limited. Adding more Potassium isn’t going to help your plants if they’re suffering from inadequate lighting or a lack of CO2. This is where the majority of supplement regimes go wrong. They attempt to supplement individual nutrients without looking at the system as a whole.

pH Effects On Availability

pH also affects the availability of certain nutrients. Trace elements, particularly iron, become less available as pH increases (Aquarium Lesson). If your tap water is hard and alkaline you may notice signs of iron deficiency in your plants even if your aquarium has more than enough iron. This is actually an instance where aquarium plants benefit from iron supplements – but only if you’ve determined that pH is the limiting factor.

Once you understand how different nutrients affect plant growth you can begin to decipher the marketing speak on supplement bottles. “Grow faster with enhanced trace elements” could be exactly what your hard, alkaline tap water aquarium needs. The exact same bottle could be completely useless in your aquarium that’s actually limited by light or CO2.

Liquid Fertilizers vs Root Tabs vs Individual Supplements

Now you understand how nutrients work you should have a better idea about which type of supplements you actually need.

Liquid Fertilizers are applied directly to the water column and absorbed by plants through their leaves. Any plant with relatively thin leaves can make immediate use of liquid fertilizers dosed into your aquarium. Most stem plants, floating plants and species like Vallisneria fall into this category. Faster growing tanks will usually require daily dosing of liquid fertilizer. Slow growing tanks can get away with once or twice weekly applications (2Hr Aquarist).

Root Tabs slowly breakdown in your substrate and feed plants that gather the majority of their nutrition from their roots. Slow, methodical release of nutrients makes root tabs ideal for heavy root feeders like large Echinodorus species or Cryptocoryne. They’re also ideal for aquarium plants that have thick leaves which aren’t efficient at absorbing water column nutrients. These include many species of Anubias and Java Moss. Using root tabs is also a common way to fertilize tanks with inert substrates like sand or aquarium gravel.

Individual Supplements allow you to target specific nutrients. They can be useful for addressing known deficiencies or providing plants with nutrients they require in higher concentrations. Iron supplements are helpful for high-pH tanks and plants that require extra iron for colouration (think red plants). Potassium can be used to supplement soft water aquariums that naturally have low concentrations. Trace element supplements can come in handy if you use RO water or know your tank is low on specific micronutrients.

Again, the key to using these effectively is understanding what your plants need and what they don’t. If your plants are already potassium limited then adding more potassium won’t do anything to improve your tanks growth rate.

Evaluating Your Aquarium’s Nutritional Needs

It’s difficult to give blanket advice about what your tank needs and what it doesn’t. A lot of it comes down to the conditions your tap water naturally contains and your individual aquarium setup.

The UK has some of the best tap water for plant aquariums in the world. Almost all areas of the UK have enough calcium and magnesium for plants to thrive. Hard water areas tend to also have plentiful trace elements but struggle with high pH limiting iron availability. Soft water areas usually require more supplementation but don’t experience pH limiting as often.

The best way to really understand what your aquarium needs is by…

Testing Your Water – Get a pH, GH and KH test kit. Learn exactly what you’re working with before you make any decisions. Take it a step further and use nutrient test ranges for planted aquariums to test the baseline amounts of Nitrogen, Potassium and Iron in your tap water. You can use these as a baseline to compare with the nutrients your plants consume over time by testing your tank water a few weeks after you set up your aquarium.

Looking For Clues in Plant Growth – Are your plants taking off like crazy or did you build the tank and they refuse to grow? Yellowing leaves can indicate nitrogen deficiency but could also just be older leaves dying off naturally. Iron deficiency also causes yellowing leaves but remains green along the veins. Yellow leaves with green veins that become completely yellow as they die are likely suffering from inadequate lighting or poor root health.

Tracking Growth Over Time – Sunny tanks that are properly dosed tend to grow very quickly once plants get started. If your plants have flourished since you set up your aquarium but are recently experiencing issues, nutrients are likely the issue. Long term lack of growth since you set up your aquarium is more likely a lighting or CO2 problem.

Considering Age and Stocking of Tank – A brand new tank that you’ve planted but don’t intend to stock heavily is going to benefit from full fertilization. There aren’t many natural sources of nutrition in a new tank and your plants will appreciate all the help they can get. A properly stocked tank with a decent fish population may require very little supplementation. Fish waste produces plenty of nitrogen and phosphorus. Heavily stocked tanks may benefit from potassium supplements and possibly extra trace elements but are unlikely to need extra nitrogen.

There’s no perfect way to evaluate your tanks needs but using a few or all of these methods can help you make more informed decisions about where to spend your money.

Common Aquarium Supplement Mistakes That Cost You Money

• Mistake #1: Thinking of supplements as plant medicine. It’s easy to think that because your plants aren’t growing well you need to supplement them with nutrients. Unfortunately, plants don’t respond to nutrients the way people do medications. Poor plant growth is often tied to lighting, CO2, or water quality issues that no amount of fertilizer will correct. Adding supplements to fix a non-nutritional problem is just wasting your money.
• Mistake #2: Buying single supplements without testing. Iron is a popular supplement because iron deficiency is easy to spot. But did you know that tons of aquariums are already more than adequately stocked with iron? Alot of aquariums suffer from high pH which locks up the iron that’s already in your aquarium making it unavailable for your plants to use. Adding more iron without addressing the pH won’t help your aquarium and can cause algae problems if you overdo it.
• Mistake #3: Over supplementing a new tank. New tanks take time. Don’t underestimate how slow plants will grow while your aquarium goes through the cyclical process of becoming established. Feeding a new aquarium heavily is just going to feed the algae instead of your plants. Your plants grow slowly at first not because your missing nutrients but because they’re growing roots and getting used to your water conditions. Start slow and increase fertilizer amounts as your plants begin to grow.
• Mistake #4: Supplement without understanding CO2 relationship. Aquarium plants require CO2, nutrients and light in fairly equal quantities. Adding extra fertilizer to a tank that’s limited by something else creates bigger problems. Let’s say you have a tank that’s struggling to grow but isn’t limited by nutrients. You add tons of fertilizer because your pretty sure that’s the problem. Your plants won’t grow any better because they’re still limited by something else. In this case let’s assume they were CO2 limited. Now your tank has excess nutrients which leads to bigger algae problems and poorer water quality. This is a very common scenario for aquariums that don’t use CO2. People think they need expensive nutrients to solve a problem that was actually caused by a lack of CO2.
• Mistake #5: Thinking more expensive means better quality. I’m as guilty of this as the next guy. Fancy premium planted aquarium supplements are basically the same as cheap grocery store brands. They just come in smaller bottles with way more marketing fluff. Compare ingredients lists and do the math to figure out which product is actually cheaper per dosage. You’ll be surprised at how many so called premium brands end up costing you more without providing any additional benefits.

The Science Behind Plant Aquarium Supplements

Scientific research into aquatic plant nutrition is fairly limited but the studies that have been done have been pretty enlightening. Studies have consistently shown that aquarium plants respond better to holistic complete nutrition rather than targeted supplement additions. Plant nutrient requirements also change based on lighting levels, available CO2 and overall growth rate.

Iron was one of the first nutrients studied in relation to aquarium plants. Research has shown that plants do require extra iron, but more isn’t always better. Excess iron tends to feed Chromonas bacteria which leads to more algae. The generally accepted range for iron is 0.1-0.5mg/L for most planted aquariums. More is required if you’re exclusively keeping red plants under intense lighting.

Research into trace element usage by aquatic plants has been limited. But the little research that is out there supports using a comprehensive liquid fertilizer or root tabs that include trace elements. These have been shown to provide all the trace elements your plants could possible need except in extreme situations. Reverse Osmosis/R/o water and very high pH.

Studies directly comparing root tabs and liquid fertilizers have come to the same conclusion. Both are effective when used properly. Plants that are heavy root feeders do better with some sort of substrate fertilization. Plants with thin leaves that efficiently absorb nutrients from the water column respond faster to liquid fertilizers. Using a combination of both tends to produce the best results.

Advice For Different Types of Aquariums

Similar rules apply to different aquascaping styles but there are always exceptions to the rule.

• High Light CO2 Scrubbed Tanks require heavy fertilization. Your plants have high metabolic demands and will use all the nutrition you can give them. These aquariums can generally afford to spend more money on supplements because their plants need it and will show growth differences.
• Low Light More Natural Styled Tanks often require very little if any supplementation. Don’t over think it. Just because you don’t see growth doesn’t mean your plants are lacking nutrition. Fast growing demanding plants don’t do well in low light environments. Choose your plants accordingly and you’ll never need to spend a dime on fertilizers.
• Nano Shrimp Tanks can still benefit from supplements but you need to be more careful about what you’re adding to your tank. Many fertilizers contain copper or other trace elements harmful to invertebrates. Its well worth buying the shrimp safe versions of fertilizer if you have inverts. Root tabs are also usually safer than liquid fertilizer because they limit the amount of nutrients your plants are exposed to.
• Quarantine and Hospital Tanks don’t need supplements. They’re not permanent aquarium setups and plant growth doesn’t matter because you’re focusing on fish health.

The Benefits of Intelligent Supplement Use

Deciding your aquarium needs supplements can open the door to some serious targeted problem solving. Maybe your tap water is soft and your aquarium would benefit from potassium supplements. You’ve got a high pH freshwater tank struggling to grow red plants? Iron supplements might do the trick.

Individual aquarium supplements allow you to customize your aquarium’s nutrition and dial in on exactly what your aquarium needs. You also have complete control over dosing. You can easily increase or decrease the amount of supplement you’re adding based on season changes, plant growth cycles and even changes to your fish stocking.

Taking the time to figure out what your aquarium needs means you spend money on things you know will help. Instead of blindly spending money on expensive premium brand aquarium supplements you can find cheaper alternatives that do the exact same thing.

Plant growth in your aquariums will improve when you address actual limitations. Enough dosing of the correct supplements will allow your plants to out compete algae and stay healthier longer. This means less maintenance for you and more time enjoying your aquarium.

Implementation Strategy

Knowing what you need is only half the battle. Learning how to actually spend your money effectively can help you save even more.

Phase 1 – Determine The Needs Of Your Aquarium (1-2 weeks)

Start off by getting a test kit. At a minimum you’ll want a pH test kit and General Hardness test kit. Test your tap water and take note of the results. Do your research, look at your plants and see if you can determine if you’ve got mostly water column feeders or root feeders.

Estimated Budget:

• pH and General Hardness test kit – £8-12
• Basic plant fertilizer – £15-25
• Your time spent researching – £0

Grand Total – £25-40

Phase 2 – Buy what you need and start experimenting (weeks 3-6)

Using the information you already know about your aquarium and the plants you chose during Phase 1 go out and buy what you need. Maybe that means comprehensive liquid fertilizer, root tabs or just individual supplements. Don’t over do it you can always add more later. Start slow and pay attention to how your plants react. Keep a log if you have to.

Estimated Budget:

• Quality liquid fertilizer or root tabs – £20-35
• Iron supplement if your tanks needs call for it – £8-15
• Nutrient test kit if you don’t already have one – £15-25

Grand Total – £45-75

Phase 3 – Continue optimizing your aquarium (Months 2-3)

React accordingly. If your aquarium could use some potassium try adding a potassium supplement. Your plants haven’t responded? Take another look at your aquarium. Are you sure they need more nutrients? Did you miss something? Maybe your plants would grow better with better lighting or a CO2 system. The options are endless but once you know your limits you’ll waste less money trying to figure out.

Estimated Budget:

• Any additional supplements you find your aquarium needs – £15-30
• Replacement supplies (test tubes, nutrients, etc.) – £20-35

Grand Total – £35-65

In reality you’ll probably never need to go beyond phase 2. And many aquariums don’t even need any supplements at all. You know your aquarium better than anybody. The trick is knowing when spending money on plant nutrients is actually going to solve a problem. And when you’re just going to waste money trying to fix something that won’t be fixed by throwing money at it.