Cones in the aquarium: Filled with potential- and questions?

Leaves, wood, botanicals...there sure are a lot of different things we can put into the water in our aquariums to impact the color and chemical characteristics of our aquaria! Many botanicals perform similarly, in my experience, with some varieties slowly releasing tannin and humic acids into the water. Other varieties of botanicals, such as leaves, palm products, and today's subects- cones- can quickly and efficiently impart these substances to the aquarium water once submerged.

Cones, such as Alder and others, have been used successfully for quite a few years by shrimp and fish breeders to lower the pH in their aquaria, as well as to stimulate breeding. Some claim that they provide some antifungal properties. I've seen claims of higher hatch rates for certain fish eggs when utilizing cones as "water conditioners" in spawning aquariums. Is there any merit to these claims? Well, there seems to be at least some anecdotal evidence that the cones (well, really- the humic substances that cones release) may offer some benefits. More about this later.

What, exactly, is a "cone?" To many of us "city folks", cones are those odd-looking things that fall off big old Pine trees in yards and parks, are cool to throw into the fire while camping ('cause they "crackle!"), and at each other when you're a kid! Well, to science, a cone (known to botanists as a strobilus) is the organ on a plant that contains the reproductive structures.

At this point, I'm so tempted to make some sort of juvenile sounding joke about how weird it was that we used to throw pine cones at each other- but I'll spare you. Anyways, cones come in male and female varieties, are well-studied by scientists, and have definitive charchteristics that make identifying each species. sex, and viability possible, but I won't bore you with those details right now!

So, as far as cones are concerned, as aquarists, we like them because they contain those tannins and humic acids. As you know, here at Tannin Aquatics, we have a more than causal interest in stuff that "tints" the aquarium water and contributes to a more dynamic physical and aesthetic aquarium environment- and cones can make some important contributions.

First off, the varieties that we use are Alder, Birch, and Casauarina. These have been used for aquariums for some time, each has their own "tint capability" and therefore, utility for our purposes! 

Alder cones are probably the "alpha dogs" of the cone-using world, and you'll find aquarists worldwide playing with them in their aquariums. Hailing from the genus Alnus, there quite a few species found worldwide. The ones most commonly used in aquaria come from Northern Europe, and I think this is simply because the most adventurous aquarists- or at least the first aquarists to really experiment with them- came from this region.  Alder trees are known to have bark rich in tannins, so it's no stretch to conclude that the woody little cones also contain some tannins as well!

Now, Alder cones are small- typically only a few centimeters in length, varying by age and species- but they are powerful little "tinters!' It only takes a small amount of these guys, steeped in water, to produce some decent color.  A study done a few years back by a Swedish hobbyist using from one to six cones in a glass containing about 10 ounces of tap water, with a starting ph of around 8.12, was able to affect a drop to 6.74 with one cone after about two weeks, 4.79 with 2 cones after two weeks, and an amazing 3.84 with 6 cones after the same time period! The biggest part of the drop in pH occurred in the first 12 hours after immersion of the cones!

This same enthusiast extrapolated that it would take about 330 cones to lower the ph of 100 liters of tap water from 8.12 to a respectable 6.74 in about 2 weeks, with nicely "tinted" water resembling, in the hobbyist's own words, "a cup of tea"- music to our ears, of course! So, suffice it to say, these little cones pack a considerable wallop! Of course, no hobbyist I know is going to toss 300 alder cones in a 25 gallon aquarium to try to drop the pH by 1.38, but this exercise demonstrates the "capabilities" of these innocuous-appearing little cones, and demonstrates the need to treat them with some respect and start very slowly when using them in our aquaria!

The other cone commonly used by fish geeks is the Birch cone (Betula sp.), which has similar, although not quite as pronounced an effect on pH as Alder, in our rudimentary recreation of the other guy's slightly more sophisticated tests! Birch cones are a bit larger, more elongated, which apparently doesn't have much relation to their "capabilities" as a pH reducer in the aquarium. Birch extracts (from the wood, mainly) are used in other industrial capacities, such as treating leather and in flavorings.

A given quantity of Birch cones do seem to render a slightly darker tint to the water than Alder, in our opinions, but as we know, tint is NOT necessarily indicative of the pH of water. And remember, very hard water is unlikely to have the pH substantially influenced by a reasonable amount of any cones or botanicals. Softer water (like RO/DI), with little to no general hardness, is far more susceptible to pH manipulation via botanicals, in our experience.

In order to round out our collection of cones, we have sourced the rather attractive Indian Casuaurina Cone (Allocasuarina and Alnus sp.), which come from the beautiful evergreen trees found throughout Australia, Oceana, and as non-native introductions into the Indian sub-continent(which is odd, considering the common name, right?). These cones are somewhat less known in the hobby in Europe and North America, but have apparently been used in Asia for a number of years in the same capacity as Alder has in Europe. These are handsome, "fat-looking" cones that actually look kind of different to us.

As much as I love using cones for aquariums, I must admit that, in my opinion, they hardly look "tropical", and are best relegated to the utilitarian role of "media", used to influence tint, and to a lesser extent, pH of the aquarium water in filters or media bags away from the display. That being said, I've seen them used to great aesthetic effect by other, more talented lobbyists, like my friend James Sheen, who incorporated them into his display beautifully! We've been offering cones for some time, and our customers give us much positive feedback. We've even created a "sampler" of the three varieties that we offer, so you can experiment with them yourself, and contemplate their aesthetics. 

A lot of hobbyists- especially shrimp and Apisto enthusiasts, DO like the look of cones in their displays. And, if you're going to keep cones in your display aquarium, the Casuarina are the best candidates for the job, IMHO! Their ability to reduce pH is not quite as pronounced as Alder, or even Birch; nonetheless, they can impact water chemistry and definitely can influence the tint of the water! We've arrived at using around 6 cones for every 10 gallons of aquarium capacity, but that is OUR conclusion based on our own experimentation- your "mileage", as they say, will vary.

In general, cones seem to be ideal candidates to use in filter, media reactors, or just passively somewhere in your aquarium where water flows over them gently. With shrimp keepers, they certainly make a great foraging area, and the many "faceted" surfaces (known, interestingly enough as "scales" to botanists) do a respectable job of recruiting biofilms. Since shrimp and some catfish (I'm thinking Otocinculus) seem to love foraging in them, one could conceivably sneak in some pelleted foods into the scales, turning them into unorthodox, yet effective "feeding stations" for these animals!

In general, the cones mentioned here are known to science to have rather significant amounts of tannins in their tissues. Their usefulness as aquarium "media" is easy to understand. However, the properties attributed to them by aquarists is a bit harder to substantiate. Many hobbyists who use cones will speak of their alleged "anti-fungal" and "antibacterial" properties, with little more than anecdotal experience (or less!) to substantiate these claims. Unlike Catappa leaves, which have been studied by scientists in Asia and elsewhere for fisheries use as antifungals/antimicrobials, and which DO have some phytochemical constituents that may be useful in treating and preventing infections, we're really operating on the basis of inference and supposition that, because the cones seem to do what leaves do from a pH and aesthetic standpoint, that they must also have these "therapeutic" capabilities, right?

Of course, those of us who trade in botanicals need to be responsible when assigning these "attributes" to the stuff we sell, and not everyone in the industry does. I see lots of vendors selling these items around the world, with descriptions that absolutely imply that the cones have these capabilities and should be used to treat fungus, hatch eggs, etc., I don't think that such blanket statements are responsible. As much as I would love to share their enthusiasm and faith that they do these things, until scientific aquarium-use-specific research is done on them, I think it's best to offer them as a means to provide some tint to the water, some pH-reducing capability, and state that it is thought by some to have possible therapeutic benefits for aquatic animals, the extent of which is not fully understood.


All buzzkill aside, I would encourage responsible hobby-level experimentation of cones as a possible "homeopathic" remedy or "preventative" for fungus and other possible fish maladies. As long as we are open-minded, record our results, and don't simply attribute every good (and bad) thing that happens to our animals while using the cones to their "properties", it is certainly with looking into! The number of shrimp breeders and Apsitogramma breeders I've spoken with and read about who do use cones (mainly Alder) in their breeding/rearing aquaria and imply good results makes it too tempting to simply dismiss!

All in all, I hope this brief foray into the world of cones in the aquarium has at least inspired you to check them out for yourself!

Stay open-minded, yet skeptical. Stay enthusiastic, but grounded.

And most important...

Stay Wet!

Scott Fellman

Tannin Aquatics





Scott Fellman
Scott Fellman


4 Responses


September 18, 2023

Coniferous trees generally have lots of resin, not good for our tanks.

Scott Fellman
Scott Fellman

October 16, 2019

I have no experience with “almond” other than Terminalia catalpa, the “Indian Almond” tree… I would just test them carefully!


Nejat Salih
Nejat Salih

September 24, 2019

Is it possible to use normal almond tree leaves
Instead of cattappa leaves

Gert Botha
Gert Botha

March 12, 2017

Dear Mr. Fellman
Thank you for your wonderfull inspiring article!
Being an aquarium freak ever since I can remember(and ONLY a hobbiest and no professional) I always wanted to experiment with pine cones!
Not really getting the answers I searched for, I now am willing to give it a try!
I haven’t got alder cones, but only the big ones from South African needle pine trees. So I will first test!
In the mean time I know a stable ph is far better than the “correct” one that is fluctuating! Hence my first question…. Can I see the genaral use of cone as a good buffer then?!

Once again many thanxzzz for your article and many regards from Namibia

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