Your aquarium plants might be struggling, but the solution could be growing right out of the top of your tank. If you have ever battled persistent algae or worried about fish health, you have likely searched for ways to use pothos to lower nitrates in aquarium setups. This common houseplant is not just for decoration; it is a powerful, natural filter that many aquarists swear by.
Nitrates are the end product of the nitrogen cycle. While less toxic than ammonia or nitrite, high levels stress fish and fuel algae growth. Water changes help, but they are not always enough. Adding a pothos cutting is a simple, low-cost way to tackle the problem at the source.
In this guide, you will learn exactly how this plant works, how to set it up, and what to expect. You will also find practical steps to avoid common mistakes. Let’s get straight to the point.
Why Nitrates Build Up In Your Tank
Fish waste, uneaten food, and decaying plant matter all produce ammonia. Beneficial bacteria convert that ammonia into nitrite, and then into nitrate. In a closed system, nitrates have nowhere to go unless you remove them manually.
Most tap water already contains some nitrates. When you top off evaporated water, you add more. Over time, the concentration climbs. Regular water changes are the standard fix, but they only dilute the problem temporarily.
Live plants consume nitrates as fertilizer. However, many aquatic plants grow slowly. Fast-growing stem plants help, but they need high light and CO2 to keep up. This is where a terrestrial plant like pothos becomes a game changer.
Pothos To Lower Nitrates In Aquarium
Pothos (Epipremnum aureum) is a vine native to French Polynesia. In the wild, it climbs trees and absorbs nutrients from the air and rain. When you place its roots in aquarium water, it adapts quickly. The roots act like a sponge, pulling in nitrates, phosphates, and other dissolved organics.
Unlike submerged aquatic plants, pothos grows emersed. This means the leaves stay above the water line. Because it has unlimited access to atmospheric CO2, it photosynthesizes at a much faster rate. Faster growth equals more nutrient uptake.
Many hobbyists report a noticeable drop in nitrates within two weeks. Some even remove mechanical filters entirely because the plant does the heavy lifting. It is not a magic bullet, but it is one of the most effective natural methods available.
How Fast Does Pothos Remove Nitrates?
Speed depends on several factors. Light, temperature, and root mass all play a role. Under moderate light, a healthy pothos can absorb a significant portion of the nitrate load. In a heavily stocked tank, you might see a 20-30% reduction in a week. In a lightly stocked tank, the drop can be even more dramatic.
Keep in mind that pothos also consumes other nutrients. It will compete with algae for phosphates and trace elements. This often leads to clearer water and less green film on the glass.
What Are The Signs It Is Working?
You will notice new white roots growing from the nodes. The leaves will perk up and may grow larger. Your test kit will show a steady decline in nitrate readings. Algae growth will slow down, especially green spot algae and hair algae.
If you see yellowing leaves, that is a sign of nutrient deficiency in the plant itself. This is rare in an aquarium, but it can happen if the water is too clean. A small dose of liquid fertilizer for the pothos can fix that.
How To Set Up Pothos In Your Aquarium
Setting up pothos is easier than you think. You do not need any special equipment. Just a cutting, a place to secure it, and some patience. Here is a step-by-step guide.
Step 1: Choose The Right Cutting
Take a cutting from a healthy pothos plant. Cut a vine that is at least 6 inches long. Make sure it has at least two or three leaves and a node (the brown bump where roots grow). Remove the bottom leaf so the node is exposed.
You can root the cutting in water first, or place it directly in the aquarium. Rooting in a glass of tap water for a week helps it develop a small root system. This reduces the risk of the cutting rotting in the tank.
Step 2: Secure The Plant Above The Tank
The leaves must stay dry. Submerged leaves will rot and die. Use a clip, a suction cup, or a piece of aquarium-safe string to hold the stem to the rim. You can also use a plastic plant holder that attaches to the glass.
Make sure the node and any new roots are submerged. The stem should not be buried in the substrate. Pothos roots are fine floating in the water column. They do not need to be planted in gravel or sand.
Step 3: Position For Light
Pothos needs light to grow. If your aquarium light is strong enough, it will reach the leaves above the rim. If not, place the plant near a window or add a small clip-on grow light. Too much direct sun can burn the leaves, so indirect bright light is best.
Do not worry about the light affecting the tank. The plant will use the same light that your fish and aquatic plants need. There is no conflict.
Step 4: Monitor And Maintain
Check the roots weekly. Trim any that turn brown or mushy. Rinse the roots during water changes to remove debris. As the vine grows, you can train it along the wall or trim it back to keep it tidy.
Replace the cutting if it stops growing. Most pothos cuttings last for years, but they can become woody and less efficient over time. A fresh cutting will always be more vigorous.
Best Practices For Maximum Nitrate Reduction
To get the most out of your pothos, you need to optimize the conditions. Here are some practical tips that go beyond the basics.
- Use multiple cuttings: One cutting helps, but three or four will make a real difference. The more roots you have, the more nitrates you remove.
- Keep water flow around the roots: Place the roots near the filter output. This ensures they get a constant supply of fresh water and nutrients.
- Do not clean the roots: The roots develop a biofilm of beneficial bacteria. This biofilm also processes waste. Rinsing too aggressively removes this helpful layer.
- Combine with water changes: Pothos is not a replacement for water changes. It reduces the frequency, but you should still change 10-20% weekly.
- Watch for potassium deficiency: Pothos absorbs potassium heavily. If your aquatic plants start showing holes in leaves, add a potassium supplement.
What Fish Are Compatible With Pothos Roots?
Most fish ignore the roots. However, some species may nibble on them. Goldfish, cichlids, and silver dollars are known to taste-test new plants. If you have these, protect the roots with a mesh bag or a plastic guard.
Shrimp and snails love pothos roots. They graze on the biofilm and find shelter among the fine root hairs. This makes pothos a great addition to a shrimp tank. The roots also provide a spawning site for some egg-laying fish.
Can Pothos Harm Your Fish?
No, pothos is not toxic to fish. The leaves contain calcium oxalate crystals, which are toxic to pets if eaten. But fish do not eat the leaves because they are above the water. The roots are safe and do not release any harmful chemicals.
One risk is using a cutting that has been treated with pesticides. Always wash the cutting thoroughly before adding it to your tank. A quick dip in a mild bleach solution (1 part bleach to 20 parts water) for 30 seconds, followed by a rinse, can remove any residues.
Common Mistakes To Avoid
Even experienced aquarists make errors with pothos. Here are the most frequent issues and how to avoid them.
- Submerging the leaves: This is the number one mistake. Leaves will rot and pollute the water. Always keep them above the rim.
- Using a cutting with no node: A leaf alone will not grow roots. You need a node for root development.
- Placing in a dark corner: Without light, the plant goes dormant and stops absorbing nitrates. Give it at least 6 hours of light.
- Overcrowding the tank: Too many roots can reduce water circulation and create dead spots. Keep the root mass to about 10-15% of the tank volume.
- Ignoring the roots: If the roots turn black and slimy, they are rotting. Remove the cutting, trim the affected roots, and restart.
Why Are My Pothos Leaves Turning Yellow?
Yellow leaves usually mean overwatering (in soil) or nutrient deficiency (in water). In an aquarium, it is often a lack of nitrogen. Yes, the plant can consume all the nitrates and then starve. If your nitrate reading is zero, add a small amount of liquid fertilizer.
Another cause is too much light. If the leaves are exposed to intense direct sunlight, they can bleach. Move the plant to a spot with indirect light. Also, check for root rot. Brown, mushy roots will not absorb nutrients, leading to yellow leaves.
Pothos Vs. Other Nitrate-Reducing Plants
You might wonder if pothos is better than duckweed or hornwort. Each has pros and cons. Duckweed grows fast but covers the surface and blocks light. Hornwort sheds needles and can be messy. Pothos is clean, easy to remove, and does not overrun the tank.
Pothos also has an advantage over floating plants. It does not compete with your aquatic plants for surface light. The leaves are above the water, so your submerged plants get full light. This makes it an ideal addition to a planted tank.
How Many Pothos Cuttings Do You Need?
A good rule of thumb is one cutting per 10 gallons of water. For a 20-gallon tank, use two cuttings. For a 50-gallon tank, five cuttings. This provides enough root mass to make a measurable impact on nitrate levels.
If your tank is heavily stocked, double that number. More fish produce more waste, so you need more roots. You can always trim the roots if they grow too large. They do not harm the fish, but they can clog the filter intake if they get too long.
Does Pothos Affect PH Or Hardness?
Pothos does not significantly alter pH or water hardness. It consumes nitrates, which are slightly acidic. Removing them can cause a very slight pH rise, but this is rarely noticeable. It also absorbs some calcium and magnesium, but not enough to affect hardness.
If you have soft water, you might see a small drop in general hardness over time. This is because the plant takes up minerals. Regular water changes will replenish these. Test your water weekly to stay on top of any shifts.
Frequently Asked Questions
Can I Put Pothos Directly In The Aquarium Water?
Yes, but only the roots and stem should be submerged. The leaves must stay above the water line. Use a clip or holder to keep the plant upright. If the leaves stay wet for long periods, they will rot and harm the water quality.
Will Pothos Remove Nitrites And Ammonia Too?
Pothos primarily removes nitrates. It can also absorb some ammonia and nitrite if they are present, but it prefers nitrate. Your biological filter should handle ammonia and nitrite. Pothos is a supplement, not a replacement for your filter.
How Long Does It Take For Pothos To Show Results?
You will see new root growth within a few days. Nitrate reduction usually becomes noticeable within 1-2 weeks. The exact time depends on the plant’s size, light, and your tank’s bioload. Be patient and test your water regularly.
Is Pothos Safe For All Aquariums?
Pothos is safe for freshwater tanks. It is not suitable for saltwater aquariums because the salt will kill the plant. It is also not ideal for tanks with very high water flow, as the roots may get damaged. Otherwise, it is a versatile and hardy plant.
Can I Use Pothos In A Tank With No Fish?
Yes, you can. In a fishless tank, the plant will still grow, but it will not have a steady supply of nitrates. You may need to add a small amount of fertilizer. It can also help cycle a new tank by providing surface area for beneficial bacteria.
Final Thoughts On Using Pothos
Adding pothos to your aquarium is one of the smartest moves you can make. It is cheap, easy, and highly effective. You do not need to be a plant expert to keep it alive. Just give it light, keep the leaves dry, and let the roots do the work.
Remember to test your water before and after adding the plant. This will show you exactly how much it helps. You might be surprised at how quickly your nitrate levels drop. Many aquarists never go back to relying solely on water changes.
If you have struggling plants or persistent algae, give pothos a try. It is a natural, sustainable solution that benefits both you and your fish. The plant will grow with you, and your tank will be healthier for it.
Start with one cutting today. In a month, you will see the difference. Your fish will be more active, your water clearer, and your maintenance routine lighter. That is the power of a simple houseplant.