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What's Wrong with My Aquarium Plants?

Updated: Apr 10

Building your own planted tank with thriving plant life is a work of art and can be incredibly rewarding. However, many aquarium hobbyists underestimate how much time and dedication it takes to actually do it right. The main issue is that not only do you need to provide your live plants with sufficient light and space to grow, but you also need to ensure that they receive enough nutrients to thrive. Like aquarium fish, live plants cannot thrive unless all of their basic needs are met. Unfortunately, many aquarium hobbyists do not understand these basic needs and, thus, they end up experiencing problems with keeping their plants alive.



If you’re one of the aquarium owners that hope to cultivate a thriving tank then it would be beneficial for you to familiarise yourself with these common problems so that you will be able to avoid them. In the event that you do experience one of these issues in your tank, you’ll then be well-equipped to handle it properly. We’re going to lay down some of the most common problems you can run into when caring for freshwater aquarium plants and give you tips and advice on how to combat them.


Leaves turning Yellow

The first issue you might run into is having your plant leaves start to turn yellow. Live plants are available in a range of colours but more often than not they’ll be green. If your plants start to turn yellow this could indicate that there's a problem with your tank water conditions. Live aquarium plants, like most plants, undergo photosynthesis and use light as an energy source to start this biological process. Without enough light, your aquarium plants won't be able to thrive and they may even turn yellow as a result of not being able to start the photosynthesis process. Novice aquarium hobbyists often find that they’ve underestimated just how much light their plants need and they turn yellow because their previous environment at the pet store was better lit.


An alternative problem that results in your plants turning yellow could be a lack of nutrients getting to the plants, or not enough to maintain all of the plant if they’ve grown with very good access to nutrients and light. If you plan on keeping more than a couple of plants then you need to consider using some fertilizer under the substrate for your plants. By using a plant orientated substrate underneath your regular substrate, this means you get to keep your aesthetic but the plants also get to feed properly. What’s more, often these substrates for plants contain live bacteria which is beneficial to the tank because they help to turn fish waste into plant food. One that we recommend is Eco Complete.



Plant growth rate issues

When we talk about issues with growth rate in your plants it can really be two problems - either your plants are growing too slowly or they are growing too quickly. It’s most common that your problems with growth rate are that your plants are growing too slowly and this is often due to a lack of decent lighting, nutrients or carbon dioxide. These are the 3 ingredients to the recipe of photosynthesis. Run tests on your tank water and have a look at your set up. Have you got a lighting system that provides at least 3 to 5 watts of full spectrum light per gallon of water? You will also benefit from having a layer of fertilizer in place underneath your aquarium substrate. Can you check the CO2 level in your tank to rule that out? Installing extra lighting is quite easy, adding fertilizer is a little harder but still fairly straight forward. However, if your issue is the CO2 level of the aquarium water this might be a little harder to fix. If your fish aren’t enough then consider adding another, however never go above the rule of 2 gallons of water per 1 inch of fully grown fish. You may need to add a CO2 injector to improve the CO2 levels.


Alternatively we also want to cover the opposite issue of your plants growing too quickly. If you have too many plants in your tank or you’ve stocked specifically fast growing plant species then it won't be long before they begin to take over your tank. Having a large amount of plants in the tank isn't necessarily a negative thing because it keeps oxygen levels in your tank high, however once they get large enough they can become detrimental in that they can harm the appearance of your tank and start to limit swimming space for your fish.


To control this growth of your aquarium plants, just try pruning them back a little bit every once in a while. You can either discard them or you can transplant them to other parts of your tank or other peoples tanks too if you're using moss for example. Consider replacing your fast growing plants with slower alternatives or introduce a fish to your tank that likes to nibble on your plants. You can also check your setup to determine whether your lighting might be a bit more intense than you actually need. You can also cut back slightly on the amount of food you give to your fish as it might be excess food sinking to the bottom of the tank which would give your plants extra nutrients to cause this excessive plant growth.




Black algae on your plants

An issue for many people is that their plant leaves turn black, however some fail to realise that this actually may not be the plants themselves turning black. It's possible that the dark growths on the plant leaves are actually growths of algae. In cases such as this, the problem is a large amount of phosphates in the tank water. The three types of nutrients that are essential for plant growth are nitrogen, phosphorus and potassium and if there’s one or more of these nutrients that are available in excess it could start causing problems.


In the case of excess phosphates, photosynthesis may occur at a faster rate than usual which could contribute to excess algae growth. High phosphate levels are common in tanks that are poorly maintained, especially when aquarium lighting levels are kept too low. The key to dealing with this issue is to perform a large water change and to establish then keep a routine maintenance schedule. Replace your filter media on a monthly basis and replace 15% to 20% of your tank volume once a week. This should help to keep your phosphate levels under control, thus limiting the growth of algae in your tank and on your live plants.


Leaves developing holes

If your plants are starting to develop small holes in their leaves then eventually these could grow into the total disintegration of your plant. If this is the case, you may be dealing with what's known as crypt Rot. This is a disease that primarily infects plants that belong to the genus “Cryptocoryne”, hence the name crypt rot. The problem usually is down to water parameters changing too quickly. These plants don't deal well with rapid change in temperature, lighting or water chemistry. However there is some good news - even if the plants die back completely, as long as the roots are intact, the plant will regrow once your tank stabilizes. To encourage regrowth, perform regular water changes to help maintain a high quality to your water. Eventually your plants should grow back.


A planted tank is not significantly different from a standard freshwater tank but there are a few things you need to be aware of if you want to succeed. Keep in mind that plants are photosynthetic organisms which means they require light as an energy source to survive. Without adequate lighting and proper nutrients, your live plants will never thrive. Do yourself and your fish a favor by setting up your planted tank properly the first time with fertilizer under your aquarium substrate and adequate light, then you will be less likely to experience these common issues.



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