You already know that we're pretty obsessed with leaves in our aquariums, right?
One of the more recent additions to our "rotation" has been the lovely Magnolia leaf.
Yeah, the Magnolia,
Talk about an interesting subject for a botanical! The genus Magnolia has over 200 members, distributed all over Asia, the Americas, and the West Indies. It's an incredibly diverse, beautiful genus of trees.
We have offered the lovely seed pods of Magnolia for use in vivariums for some time here at Tannin Aquatics, and they've been extremely popular!
For our purposes, of course, it's important to see if the leaves are safe with fishes before we even consider using them in our aquaria, let alone, offer them for sale! If you troll online forums, you'll see the full gamut of discussions, ranging from "They killed my Apistos!" to, "I've used them for decades without any issues!" The reality is, that like any botanical or plant material used in an aquatic setting, if you prepare them, clean them, and add them gradually to your aquarium, you shouldn't have any issues.
Ahh, but I digress. More on that later.
First off, the species we're typically using here in the United States is Magnolia grandiflora, and it's a beauty! They can vary widely in color, including oranges and browns, which makes them particularly attractive for a leaf litter bed! There are over 50 cultivars of this species alone, so without being a full-on botanist, let's assume that, at least superficially, they are all more-or-less the same for our purposes. (I can hear my college Botany professor cringing right now...LOL)
Morphologically, Magnolia leaves have a distinctive look. Let's just say that, when you remove them from the context of the tree, they're downright "exotic-looking', perfect for our uses! They are rather heavy leaves, which is great news, because it means they'll last a lot longer in a submerged state, meaning that you don't need to replace them as often as you would, say, Catappa or even Guava.
They have a waxy coating which renders them more resistant to damage from salt and pollution. I'm going out on a limb and hypothesizing that it's this "waxy coating" that might be the source of some of the concerns we have about using these leaves in aquariums. The waxy covering on the leaves is called the "cuticle". It is composed of cutin, a wax-like material produced by the plant that is chemically a hydroxy fatty acid. The purpose of this covering is to help the plant retain water and repel pollutants.
Magnolia grandiflora produces phenolic antimicrobial chemicals, compounds called coumarins and sesquiterpene lactones, which discourage predation and grazing by terrestrial insects. Coumarins have known anti fungal properties. I can't help but wonder if these same antimicrobials and antifungals might-might provide some sort of benefits to fishes in a similar fashion to those found in Catappa, but this is just conjecture on my part; I am not aware of any scientific study on the matter, nor of the existence of data to confirm this theory. Let's just say that they do not seem to present any harm to our beloved aquatic pets.
Magnolias are not known to be poisonous to cats, dogs or other animals. Now, can we assume that they are safe for fishes, which would be continuously exposed to anything leaching from the leaves in the aquarium? No. However, in almost a year of personal testing, and in the experience of a number of long-term users of these leaves (whom I trust and know to be highly competent aquarists keeping many varieties of fishes), there have been no fish losses that can be attributed directly to the use of these leaves.
In my opinion, and based on the above experience of myself and others, the real danger of these leaves would be from external pollutants (soot, garden chemicals, and other surface pollutants that would accumulate on the leaves), rather than any particular issue caused by the leaves themselves. However, this doesn't mean that you should just toss them in your tank! Like any botanical, you should take the time to rinse, and really, soak the leaves overnight in (initially) warm or recently boiled water. This will help remove any residual surface contaminants and pollutants that may be present on leaves. Add only a few at a time to gauge the results. If you're going the route of collecting the leaves yourself for aquatic use, I would absolutely pass on any that are known to have been sprayed with any insecticides in recent years...That's just common sense.
As far as tannins in the leaves, these leaves seem to contain quite a good quantity of them, and you will get a good, golden-brown tint with several leaves in a relatively modest-sized aquarium! Of course, the extent to which they will tint the water depends upon many factors, like how large an aquarium you have, how many leaves you tossed in, and if you are using any chemical filtration media, like activated carbon, etc., which will remove tannins almost as fast as they're released!
On the subject of water chemistry and our good friends, the biofilms, the leaves do seem to contain a fair amount of residual sugars which will cause a bacterial bloom on their surfaces. This is especially noticeable at the tip of the stem. These will typically go away after a week or so, once the bacteria finish consuming the sugars in the leaves. In fact, many hobbyists who use these leaves never report such a bloom, but it's something to be aware of when using botanicals, nonetheless.
All the good juicy semi-scientific pondering aside, I can tell you from experience that these are awesome leaves to use in our litter beds! They are safe (if used with the aforementioned caveats), attractive, colorful, and long-lasting. I hope we have cut through some of the fear, clutter, and confusion that's propagating out there on "the interwebs" about utilizing these awesome leaves in our aquatic setups! Magnolia provides an amazing contrast to the other leaves that we use in our botanical-influenced aquariums, and I know you're going to fall in love with them as much as I have once you give them a try!
Stay open-minded. Stay creative. Do the research...
And Stay Wet!