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The optimal flow rate in a planted tank is something I’ve struggled and played with for years. In my 240 liter (63 gal) tank I’m growing a lot of plants and I’m confident I now understand how flow affects plants.
In a planted tank there should be enough flow to make all the plants wave slightly. If a plant is moving rapidly, the flow is too much. Use the output of the aquarium filter or a wave maker to control the flow in the planted tank. Make sure that the flow reaches all plants to provide nutrients.
It’s very important to understand what flow is and how it affects your plants. If you know what you are doing you can use flow and current in your tank to your advantage. In this article I’ll briefly cover everything you need to know, let’s dive straight in!
What is Flow in an Aquarium?
Flow, or flow rate, refers to the amount of water moving through your tank’s filter or water pump each hour. The higher your water rate is, the more flow and movement there will be in your tank.
Typically, the amount of flow needed in a tank will depend on the type of aquarium you have. For instance, large aquariums will need a higher flow rate. This way your aquarium water can circulate through your filtering device effectively and stay clean.
Flow Rate in a Planted Tank Compared to Other Tank Types
In addition, though, certain types of fish will need a higher flow rate to stay in good health. Ocean fish and large fish might even need a water pump to supply them with an adequate amount of flow. This goes for reef tanks, as well. Reef organisms will need more water flow to survive.
Still, what about planted tanks? Exactly how much flow is needed for your planted tank? In general, planted tanks tend to do better in tanks with lower water flow.
How much flow your tank needs will depend on the amount of water your tank has, though. But, I’ll get into that more in a later section of this post.
How Does The Flow Rate Affect Your Aquarium Plants?
Flow rate affects your planted tank more than you realize. In fact, without a proper flow rate, the health of your plants could be in danger. So, you want to have the right flow rate in your aquarium space. Still, why exactly is water flow so important in a tank?
Part of this has to do with tank health and cleanliness. Without water flow, it is difficult, if not near impossible to keep your tank clean. Water filters won’t filter your water on their own. They need water flow to run your tank water through its system. This way your water stays healthy and your plants live in the right tank conditions.
As I mentioned earlier, the flow also helps your plants by rinsing off any particles that have settled on the leaves of a plant. Because of this reason, make sure that all plants are moving slightly because of the current.
In short, your plant’s health hinges on the flow rate in your tank. Without a high enough water flow, the water in your aquarium will not move through your filtering device fast enough. Instead, debris and other tank filth will accumulate in your aquarium.
You could hand clean your tank, and even change the water often. But this can be difficult and annoying. In addition, your plants could suffer from a constant change in water levels and conditions. Having a good filter with a consistent water flow helps prevent these issues.
Why Exactly is it Important to Have Good Flow Rate in Planted Tanks?
Good flow rate also helps aid your plants in other areas of its health. For instance, CO2 and nutrients can be distributed through the water when the flow rate is right. Your plant needs a way to get food.
This reason is so important that I almost want to repeat it! If the flow is wrong, some plants might not have access to nutrients and CO2. Be careful there are no dead spots in your tank, caused by hard scape such as rocks and wood. Plants that are in a dead spot don’t get enough fresh water and have no access to food. Black Beard Algae (BBA) often starts growing in these kind of dead spots.
Photosynthesis does feed your plant, but other sources of nutrition must be introduced to your plant. The flow rate will ensure that your plants are fed and in optimal health. This is why it is so important to monitor and adjust the flow rate!
Still, you don’t want the water flow to be too intense. The flow rate should be high enough that your tank’s water flows well through your filtering devices. But it should not be so high that your plants start to suffer.
Too much movement in your water can actually cause harm to your plants. Additional turbulence and water agitation can damage your plant or even uproot it.
Furthermore, most plants don’t like to be in the direct path of a flow stream. So keep this in mind as you read this post and set up your planted tank.
What is an Optimal Level of Water Flow For Planted Tanks?
For planted tanks and tanks in general, you want to consider the amount of water in your aquarium. This way you can accurately calculate the water flow needed for your tank setup.
For instance, if you have forty gallons of water in your aquarium, the flow will need to be at least four times this amount. So, you would need a flow rate of 160 gallons per hour. This calculation is a base number, though.
In some cases, you can have a flow rate that is five to even six-time higher than your tank volume. This might seem high, but remember that you want to keep your tank healthy and clean.
If the output of the filter does not produce enough flow (or you can’t direct it too all places) I recommend adding a wave maker. A wave maker is a water pump that you can use to introduce more flow in your tank. I’ll show you a picture of my wave maker.
And this is a picture of my entire tank, as you can see the wavemaker is on the right.
Again, remember that if the flow rate is too low, your water will become stagnant. This will allow filth and other bacteria to accumulate in your tank water. So, don’t underestimate your tank’s flow rate and stick to the minimum calculation of 4x your gallon volume.
How to Adjust The Flow Rate In Your Tank?
As I have talked about throughout this post, adjusting your flow rate is crucial to plant and tank health. A good flow rate not only helps cycle your water properly through its filter. Flow rate can also help to stimulate biological and chemical filtration.
It is easier for good bacteria to grow in your tank water once you have the proper flow rate. Other discolorations and impurities will be taken out of your plant’s water when the flow is correct.
Still, how exactly do you adjust the flow rate in your planted tank? In this final section, I’ll go over this question in detail. This way you know exactly how to monitor and maintain the flow of your planted aquarium!
Pick A Good Filter
Adjusting the flow rate of your tank will depend on the type of aquarium equipment you have. Depending on what type of filtering device you own, changing the flow rate will be easier or harder.
For example, higher-end filters will be much easier to manage, and will likely have adjustment knobs that make it easy to change the flow rate.
Less expensive models, on the other hand, might not have this capability. So, changing the flow rate in your tank could be harder with these types of devices.
Overall, you want to choose a filter that has simple adjustment capabilities. In addition, the flow rate should be powerful enough for your tank. Especially if you have a larger planted tank you want something that will get the job done.
This way you don’t have to add any water pumps to your planted tank. Each filtering device will have a different GPH so look into any model you buy. Sponge filters have an especially low GPH for instance.
Add in Pumps if You Need More Flow
In some cases, your filtering device might not have a high enough flow rate. So, if you need to up the amount of water flow in your tank, consider getting a water pump or an air pump. I really recommend getting a wave maker if you’re struggling to get the correct amount of flow.
The one that I recommend is a rather cheap model from Sunsun. They’re super popular and very convenient. You can use the suction cup to stick it to the inside of your tank. Check out this link to Amazon for more detail. It is an affiliate link, so if you do decide to buy one you support my website with no extra cost to you. I appreciate that a lot.
Lower Flow Rate With Tank Decorations
Some filters don’t have an adjustment knob or a way for you to lower the flow rate. If you have a device like this, you can still lower the flow rate. Tank decorations are one way to minimize the flow rate in your tank.
Rocks, caves, and other large objects can be placed strategically in your planted tank. Look at where the water flow is strongest and place objects around this area of your tank. You can also put tank decorations near your plants to minimize the water flow around them.
Again, though, having a filtering or pump device that is adjustable is the best way to manage the flow in your planted aquarium!
Cover Up The Input or Output of Your Filtering or Pump Device
In addition to adding tank decorations, you could also try covering up the input or output of your filtering device. Sponges, pantyhose, and other objects can be placed near either of these locations. This will help control the flow of your water.
This is a crude way to control the rate of water flow, but it can work if your filter or pump does not have an adjustment dial or valve.