How Tannins Affect Aquarium. Pros and Cons.

How Tannins Affect Aquarium. Pros and Cons.

Driftwood, cones, leaves, and other botanicals can be a lovely addition to our tanks. They look amazing and last a long time. However, they will also affect the water in your aquarium.

After some time, you may notice that your crystal clear water turns into a light yellow to dark brown. It happens because driftwood and botanicals release tannins.

Today I’ll take a closer look at tannins, Pros and Cons, and what they mean for our tanks. You will know what they are, how they affect your fish and shrimp, and what you can do to avoid or minimize their presence in your carefully prepared aquatic environment.

Without further ado, let’s talk about tannins!

What are tannins, anyway?

When you hear mention of the word ‘tannins’, this is actually referring to tannic acid.

Tannic acid is naturally produced by the decay of things like driftwood or leaves from the plants in your tank.

Interesting fact: Although Almond and Oak leaves are probably the most popular choice in the aquarium hobby, people often forget (or simply do not know) that tannins are found in virtually all families of plants, and comprising up to 50% of the dry weight of leaves!

As it is a natural process, most aquatic animals are quite used to tannins and even benefit from their presence in the water.

Tannins do build up a little acidity and the release of tannins may also discolor the water. All these sudden changes might cause panic for someone who is new to the hobby.

Luckily, it’s not actually such a bad thing.

To that effect, let’s explore how tannins affect animals and what you can do to eliminate the chance of tannins or simply regulate them a bit if you would like your fish to have them.

Are tannins dangerous for my fish or shrimp?

No, they are not.

On the contrary, tannins are generally going to be beneficial to your animals, but you also need to understand them and the effect that they have before introducing things like driftwood to your tank.

The main reason for this is that tannins are acidic and they can reduce the PH levels of your tank. Can it be a problem?

Tannins and Water Parameters (pH and KH)

Well, if this is done too quickly, some fish and especially shrimp (shrimp do not like fluctuations in water parameters) may go into shock.

Therefore, you may have already heard that it’s important to introduce driftwood into your aquatic environments with a bit of care and a lot of careful checking of your water to avoid this possibility.

But is it really so scary? How big fluctuations in water parameters can we expect from tannins?

In reality, it is also not as bad as it may look.

Even though it is true that wood can contribute acidic byproducts to the surrounding environment, these acids are very weak.

Therefore, your driftwood should be massive to make an impact on your water parameters. I’d say that you may start seeing some changes if it takes at least 10 % of your water volume.

But even in this case scenario, if your Carbonate Hardness (KH) is more than 5, you will barely see any drops in our pH at all because carbonate hardness neutralizes acids (including tannins). This is essentially the buffering capacity of your water.

Aside from the PH level modification, tannins introduced into your tank will also soften the water a little bit.

This can be useful for species that prefer softened water like tropical fish or some Caridina shrimp species are actually quite a bit more comfortable in the water with a lot of tannins.

Of course, not all animals are fond of low pH and soft water, however, so you will want to consider all of the species that you are housing to ensure that your new driftwood will be a good fit for everyone living in your tank.

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Benefits of Tannins in Aquarium

So, now when we know that tannins in the water can help to recreate a natural water source for some species, what else can we expect?

  • Antioxidants and antibacterial properties

Results of the experiments showed that tannins possess antimutagenic potentials as well as antimicrobial properties. Several studies have reported on the antioxidant and antiradical activities of tannins.

Tannins improve immunity, encourage growth, and increase the lifespan of our animals.

  • Breeding rates in fish

For example, tannins from Indian Almond Leaves have a beneficial effect on the Guppies’ reproduction. Tannins from the leaves:  

  • shorten the gestation period,
  • double pregnancy rate,
  • increased the survival rate of the females after giving birth and the fry.
  • Metabolism in shrimp

As for the shrimp, tannins have macro and trace elements, which play a vital role in shrimp metabolism and molting and facilitates the acclimatization process.

  • Prevents algae development

Well, actually it is false and true at the same time. How so?

  1. Unlike popular belief, tannins do not directly inhibit algae development.
  2. However, water discoloration has a significant impact on algae growth! The darker the tank, the less algae it has. That is why blackwater aquariums with lots of tannins almost never have problems with algae blooms. It is all about the lighting. 
  • Additional food source

As driftwood, cones, leaves, etc. break down, they produce great food for fry and baby shrimp. Algae, biofilm, and lots of different microorganisms that grow on the decaying matter will also become the food.

It will help you to increase their survival rate.

Cons of Tannins

  • Color. I do understand that reddish-brown or yellowish-brown color is not for everyone. However, it is a matter of preferences. Personally, I don’t mind it at all.
  • Lowers pH. If your water has a very low buffering capacity (low KH), it can affect your water parameters. So, be a little bit more careful with that.
  • Increases TDS. The tannic acid will increase your TDS a bit as well. These small changes will not have a real negative effect but if you are a perfectionist, it may irritate you.

What can I do to eliminate or reduce tannin leakage to my tank?

If you simply do not like the way it looks and prefers crystal clear water in your tank, there are several ways to help you out.

1. Aquarium activated carbon

Activated carbon is probably one of the fastest and easiest ways to remove tannins from the water.

This filtration media product was specifically created to eliminate pollutants and contaminants such as chlorine, chloramine, tannins, etc.

So, how fast does it act?

Well, there is no formula as to how fast activated carbon can remove tannins. However, you will notice the difference in only several hours after using it in your tank.

Unfortunately, activated carbon also has some limitations. For example, it does not function very long, carbon media should be replaced regularly (once a month). In addition, it reacts with medications used for fish and/or shrimp disease treatment.

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2. Seachem’s Purigen

Seachem’s Purigen is another great adsorbent that will make short work of tannins.  

Depending on your tank’s size and tannins concentration, it may take from one to several days to completely clear up the water.

Another great thing about this product is that it can be regenerated and used over and over again.

Once you notice that the beads get dark brown or black from picking up the tannins, it is time to re-charge.

The process of regeneration is pretty simple and written on the manufacturer’s site.

Note: Out of practice, it is recommended to re-charge the bag after 2 weeks’ usage the first time around. After that, regeneration should be ok to be done every month or so.

Seachem’s Purigen – link to check the price on Amazon.

3. Cure Driftwood

If you don’t mind some tannins being in your tank (and if you have dry leaves, then you’ve got some already!), you can prepare the driftwood beforehand to minimize the amount of tannins that will be produced.

One way to help ensure that driftwood does not leach the maximum amount of tannins (thus potentially affecting pH) is to simply submerge the driftwood into a dechlorinated tank and leave it submerged for at least a week or two.

This will discolor the water a bit, turning it yellow or brownish-yellow color.

Keep in mind that this method will not remove tannins; it can only reduce the amount of tannins in your tank as driftwood decomposes naturally.

After that I would also boil the driftwood (if it is not too big) for 10 to 20 minutes at a time, changing out the water until you are no longer seeing the discoloration occurring.

At this point then the driftwood will only release minimal tannins into your tank.

4. Water changes

Regular tank maintenance and water changes will also reduce the amount of tannins in the water column. A lot of it will be gone.

However, it may take months before you stop seeing a tint of tannins.

Although, it is not a fast way it is the healthiest way to rid your tank of excessive leaching until things settle out.

5. Using Faux Driftwood

Finally, if you wish to eliminate tannins but you want the look of driftwood, then you could add faux driftwood to your tank, but you should consider just using the real thing.

How Long Will Driftwood Leach Tannins?

This is a very frequent question on forums and Facebook groups. Everybody wants to know the exact period of time. Unfortunately, it is not possible to say because different materials release different amounts of tannins, and for different periods of time.

Important: Right from the beginning I need to say that it is not possible to completely eliminate tannins. For example, driftwood will never stop leeching tannins! With time it will just decrease to a level that you do not really notice anymore.

So, the best answer I can give:

As far as how long they will release them, driftwood is pretty much going to release tannins until it decomposes.

Environmental factors determine the rate, but generally, you are looking at 1 or 2 years.

How to Keep Tannins in Aquarium

Not all people want to get rid of tannins. So, if you are one of them and want to keep the brown color, you can use:

  • aquarium peat moss in the filter or
  • rooibos tea.

Some final words

Today we’ve talked about how long driftwood will leach tannins and the answer is basically, ‘as long as it’s in there. Driftwood and leaves from your aquatic plants naturally produce tannins as they decompose, and for the most part, it is going to only have a minor effect.

Tannins from driftwood will generally not be dangerous, on the opposite, these acids are highly beneficial!

So, if you like the look of driftwood and you feel like softening up the water in the bargain, then consider adding a bit to your tank.

It’s a classic look and with many animals, those extra tannins make them feel right at home!

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