How to Add Tannins to Aquarium

Tannins are a natural substance found in many plants and foods, such as tea, red wine, and cocoa. They help keep the color of leaves on trees alive by giving them a little bit of acid. Adding tannins to your aquarium can reduce algae growth because it suppresses their ability to grow and reproduce. I think this blog will help you to know about how to add tannins to aquarium. Tannins also provide protection against nitrates that cause harmful bacteria to form. 

Tannins to Aquarium

While there are many different sources for obtaining tannins, the most common is brewing black tea because it contains more than adequate amounts of tannin needed for an aquarium environment. To prepare black tea for use as an aquarium treatment, you need only steep one tablespoon per gallon (or about 17 ounces)of water for ten minutes before adding it to the tank.

Why Add Tannins to Aquarium

A tannin-rich black tea is one of the most popular treatments to use to control algae growth. The tannins that are released into your aquarium’s water will suppress or inhibit the number of nitrates in the water, which inhibits the growth of harmful bacteria.

If you have an outdoor pond, you can also use oak bark, oak leaves, grapevines, acorns, pecan shells, coffee grinds, and other tannin-rich plants to keep your pond clean. The bigger the pieces of bark or leaf you use in preparing the tea, the more tannin will be released into your water.

Tannins are naturally acidic, so they’re often used as a water conditioner to lower the pH of aquariums and ponds. It will also make your tank more acidic, so use it with care if you have cichlids or other tropical fish that require slightly less acidic water.

Just remember it’s very important for you to use tannins in moderation because an excess amount can cause stress to your fish. If you notice any of your fish acting abnormally, immediately remove tannin from the tank. Tea has tannins in them, and hence adding tannin to the aquarium helps control algae. In addition, adding tannin to the aquarium will help reduce nitrates that create harmful bacteria causing illness among the fishes.

Materials You Needs

  • Black tea
  • Aquarium Air Pump
  • Air tubing or airline
  • Rubber band

8 Ways on How to Add Tannins to Aquarium:

Step 1: Alder Cone.

Take alder cones, rinse them thoroughly to remove any dirt or insects. Do not boil or roast these cones. Put the cones in a pot with enough water to cover them completely, bring the water to a simmer and let it steam for an hour.

Alder Cone and Rinse Them

Step 2: Oak Bark

Oak bark can be found in many home improvement stores. It is inexpensive, easy to find, and has the most tannins out of any other natural source. However, you should avoid using red oak because it contains too much tannin that will cause your water to become acidic, which causes stress for tropical fish.

Step 3: Oak Leaves

Again, you want to avoid using red oak leaves as they’re too acidic. The best type of oak leaf to use is white oak. White oak contains less tannin than red oak and will not make your water as acidic. Break the leaves up into small pieces with a pair of scissors or if they are not too bad to work with, leave them as they are.

Step 4: Japanese Knotweed

This is another common plant that should be easy to find. Japanese knotweed has a high tannin content and grows quickly in most environments. Cut off a few stalks from the knotweed and remove any leaves or other debris from the stalk. You can use larger pieces of knotweed, but it is typically best to use the smaller pieces.

Step 5: Grapevines

Break off some grapevine and remove all the leaves from the stalks. Crush them up with your fingers or a pair of pliers until they are in very small bits, then steep them just like you would black tea.


Step 6: Oak Acorns

You probably won’t be able to find oak acorns unless you live in an area where there are a lot of oaks, so this method isn’t recommended for everybody. If you do have access to them, they work just like other tannin sources and can be steeped just like black tea.

Step 7: Coffee Grinds

This is one of the easiest ways to add tannins to your aquarium. All you have to do is put a few tablespoons full of coffee grinds in a bag and place it with your fish tank filter. Discard this after about two weeks because by then, the coffee will be pretty much used up.

Step 8: Grapefruit Rinds

The easiest method is to cut up grapefruit rinds and let them sit in some warm water for a day, then discard them. The more you repeat this process, the more tannin will be added to your tank.

Grapefruit Rinds

You can also add oak honey, which helps get rid of white spots and other problems related to fish. It is not recommended to use this remedy for more than three days consecutively, though.

Once you’ve found a suitable tannin source, it’s time to add them to your aquarium. The best way of doing this is by putting the tannin material in a mesh bag and tying it onto the intake of your filter. Unfortunately, this will cause the tannin to mix with the water as it is pulled through your fish tank. You can also use a spray bottle to mist some tannin solution directly into your aquarium. Still, this method isn’t recommended due to the risk of overcrowding certain areas of water within your fish tank.

Tips and Warnings


  • Adding a mesh bag to your filter intake is the best way to add tannins.
  • If you use oak bark, make sure it’s white oak bark.
  • Different tannin sources contain different amounts of tannin. Adding too much will cause stress for fish and other problems, so be conservative when adding tannins to your aquarium.
  • It is not recommended to use this method consecutively for more than three days because the tannins will become too concentrated if it’s done for too long.


  • Oak bark can be very dangerous to pets. Make sure you keep it out of your pet’s reach if possible. Also, it is best not to use oak bark as a tannin source.
  • Do not add too much oak honey to your aquarium because this will cause the water to become acidic, and it can stress out fish.
  • Make sure you rinse all of your ingredients very well before adding them to your aquarium. If any residue is left behind, it can contaminate both the water and the tank.
  • Oak honey is not recommended for people who have fish that prefer acidic water, such as Discus.
  • Do not let your tannin source sit in water for more than 24 hours. It can go bad and contaminate your tank.

Frequently Asked Questions

Are Tannins Good for Aquarium?

Yes, Tannins are good for aquariums. They provide a large variety of beneficial effects for both fish and plants.

Tannins are found in many different types of leaves, but the most important ones to include in your aquarium tank are from oak trees and conifers. Oak leaves contain tannin compounds that can help reduce harmful algae blooms, while coniferous plants provide a source of tannin needed by aquatic organisms like fish and snails to produce their own defensive compounds.

Is Too Much Tannins Bad for Fish?

Yes, too many tannins in the water will cause fish to die. Tannins are compounds that can be found in many plants and trees. They are mostly known for their astringent taste and ability to bind with proteins, causing them to precipitate out of solution. Tannins may also adversely affect other living organisms, including bacteria, algae, and aquatic invertebrates such as snails and clams.

Tannins in the Water

Are Tannins Bad for Aquarium Plants?

No, tannins are not bad for aquarium plants. Tannins can actually be used to help maintain healthy plants in the aquarium.

Tannins are substances found in leaves of some plants like oak trees and tea that have a number of benefits for aquariums. One of these benefits is that they prevent algae from growing on the leaves and provide nutrients to algae and other aquatic organisms.

Will Activated Carbon Remove Tannins?

Activated carbon is a type of adsorbent that can remove various types of contaminants from water.

Tannins are present in the leaves of plants, and they are what give tea its flavor. They can make the tea taste bitter if they are not removed. Activated carbon is used to remove tannins from water by capturing them on its surface, but it will not remove other substances like metals or other organic compounds.


Now that you know how to add tannins to aquarium make sure not to wait too long before adding them. Aquariums come in all different shapes and sizes, so the exact amount of time it takes for your tank may vary, but generally speaking, you should be able to see an improvement within a few days or weeks if done correctly. You can also use this process on other tanks like goldfish bowls or koi ponds because they will benefit from lower pH levels as well! Happy fishkeeping!

You can also read – How to level a fish tank on carpet

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