Make the most of the autumn season by collecting leaves for use in your aquarium and discover the benefits to both your fish and your bank account.
WORDS: GABOR HORVATH
When, quite some time ago, I inherited a small group of Wine-red Betta, B. coccina, I didn't know what a task and responsibility I had taken on. After a quick search of the available literature, I realised they originated from Asian peat swamps and prefer soft and dark — almost black — waters with leaf litter.
As I’d never had a fish before with similar requirements, I assessed my options. The first was to buy a ready-made black water tonic to add to their tank. The second solution was to get some imported Catappa leaves and use them to recreate the natural habitat.
The final, third option was to collect fallen leaves from a nearby forest and use those instead. This latter choice was also the cheapest and as I was on a very tight budget at that time, I opted for gathering oak leaves. Fortunately, I had a week to prepare the tank for the Betta coccina, so when they arrived I greeted them with perfect water conditions.
Since then I have kept several other leaf-litter-loving fish and — especially since becoming involved with shrimp keeping — I have learned a lot about the different leaves and their potential uses in the aquarium. So, I’d like to offer you some guidance on choosing and using them in your fish or shrimp tank.
Many leaves will give the aquarium water a tea-coloured hue. Image by George Farmer.
The benefits of leaves
Many of our favourite fish originated from waters flowing through dense vegetation and forests. The constant supply of falling leaves will colour the water tea brown, sometimes almost black. One of the culprits of this is an organic compound called tannin, which can be found in different quantities in most of the dry leaves. It is also a weak acid, which can reduce the pH of the water. The tannin is most effective in very soft waters, as the buffer capacity of hard waters can easily neutralise its acidity. Most of the black water species require soft water anyway, so with a carefully selected leaf you could achieve two goals at the same time: a nice, dark water and low pH without a need to use chemicals.
As well as tannins, some leaves also contain other organic compounds that could tackle fungal and bacterial infections without the need to use medications. Catappa (also known as Indian almond or Ketapang) leaf is widely used by fish farmers and exporters in the Far-East to reduce stress and cure diseases. The leaves of the Walnut tree — if collected green and then dried — have similar effects and are very popular among shrimp breeders.
This killifish set-up includes leaf litter on the base.
Leaf litter can also help shy species, such as Liquorice gourami, Parosphromenus sp., to settle down easier. It provides perfect places to hide, especially if you are using naturally dried, curled leaves and not the flat-packed commercial ones. Even cory cats love to play hide and seek among them, often choosing the larger leaves for depositing their eggs instead of the sides of the aquarium glass.
And we mustn’t forget about the use of leaves as decor. While not everyone’s cup of tea, certain biotopes require leaf litter. If you don’t want tea-coloured water, choose a leaf that will not colour it (or boil and soak them for a while before use). For decorating reasons you have a wide choice of large (Plane tree, Turkey oak, Catappa), medium (Oak, Hazelnut) or small (Beech, Silver Birch, Hornbeam) leaves.
Leaves provide a perfect grazing ground for shrimp.
Leaves can play an important role as a grazing ground for young and adult shrimp, and Mulberry is widely known as an excellent shrimp snack. The biofilm growing on the decaying leaf surface will also be appreciated by the fry of several fish species, acting as their starter food. Fresh leaves of several plants — for example blanched Spinach, Dandelion and Stinging nettle — can also be used to feed fish and shrimp, although in this article I will concentrate on ligneous (woody) plants only.
Most aquarists in the UK have heard of the Catappa leaf and some are familiar with its beneficial effects. If asked about British tree species useful for aquaria, most will probably mention Oak or Beech, but few will have tried any others.
A couple of years ago I met Gabor Csepanyi in Hungary, who became an “advocate” of using leaves and other parts of domestic plants instead of imported ones. He believes it is a more eco-friendly and also wallet friendly option. A discussion with him and the results of Istvan Toma’s research investigating the effect of different leaves on water parameters, have opened up my eyes to see a world of local leaves with possibilities too good to miss.
So get out there, and get collecting!
Did you know?
Autumn is the perfect time to top up your leaf stock. By this time all the unwanted compounds (sap, protein, chlorophyll etc.), are removed from the dying leaves by the tree. The tannin concentration on the other hand is increased — it can be 3–4 times higher than in the green leaves.
The dos and don’ts of collecting leaves
- Don’t collect leaves from a roadside, or other polluted areas. If you live in a big city, it’s time to visit the countryside!
- Do ensure that no chemicals have been used if you are planning to gather your stock from a maintained area (like castle parks or botanical gardens). Always check with the management first. The same applies for trees located near
- farm land.
- Do pick only healthy, undamaged leaves — watch out for bite marks, discolouration or deformations.
- Do try to collect the leaves as soon as they have fallen (try to beat the rain) to avoid the bleaching out of the valuable compounds.
- Don’t collect overwintered leaves in the spring, unless you only plan to use them as decoration (but even then they will not last for long).
- Do dry the leaves as soon as you can after collection — just spread them on a tray over a layer of paper kitchen towel. I prefer curled up leaves, but if you want flat ones you need to use a press (a couple of books would do). When fully dry store them in a paper bag or box in a dry place.
Leaves with special properties
Some leaves should be picked green and then dried for storage. In this state they can store valuable nutrients or useful organic compounds, so they are mainly used as food or as an antibacterial and antifungal water treatment. But a word of warning: be very careful with the dosage of green dried leaves, as overdosing them can lead to cloudiness and a deterioration of water quality.
Leaves of the Mulberry, Morus sp., are considered among the best shrimp foods, but are also readily taken by plecs. The green leaves are high in protein and have excellent nutritional value. If used properly they will not modify the water parameters.
Walnut, Juglans regia, leaves are famous for their very positive effect on the health of fish and shrimp. They can cure bacterial and fungal diseases and reduce stress just like those of Catappa, but will not lower the pH and colour the water to the same extent.
7 of the best leaves for your tank
All the leaves listed below should be collected in the autumn after they have fallen (naturally) from the trees.
There are several oak species in the UK, ranging from the relatively small-leafed English oak, Quercus robur, to the Turkey oak, Q. cerris, with its palm-sized leaves. They differ in leaf size and shape, but all contain a relatively high level of tannin, which makes them one of the best natural pH reducers. They will also colour the water a medium brown, so they’re not a good choice if you want to keep your water crystal clear. Otherwise the oak leaf is a very easy to find and versatile option.
The Beech, Fagus sylvatica, has quite thin and small leaves, which usually only give a faint yellowish tinge to the water. It will only slightly reduce the pH. Due to its small size, it is very suitable as leaf litter for a nano or shrimp tank containing species requiring a pH that’s close-to-neutral, such as Cherry shrimp, Neocaridina species.
Despite being widely used in urban parks due to its tolerance of air pollution, not many would recognise the Hornbeam, Carpinus betulus. Its small leaves can punch over their weight: the acidifying effect is very similar to that of the Catappa leaf. You might need more Hornbeam leaves to achieve the same effect, but based on weight they can equal their Asian counterpart. They will lower the pH very quickly, so be cautious when using Hornbeam leaves, so as not to stress your livestock. The best way to do it is to drop in a couple of leaves (depending on the size of your tank) every day until you reach the desired effect. It will also give the water a nice brown shade, which is an additional bonus if you want to achieve that black water look.
Silver birch leaves.
The Silver birch, Betula pendula, is easily recognisable because of its silver-white bark. It also has small leaves, but won’t alter the pH or the colour of the water. The rigid dry leaves are very slow to decompose, making them an ideal choice if you want to keep your water crystal clear but still use leaf litter for decoration or hiding places.
If you need slightly bigger, but similarly long lasting leaves with only a mild colouring and pH lowering impact then it is worth considering the Hazel, Corylus avellana. It has thick and rigid leaves, which are usually left alone by algae eaters and shrimp, so can serve as a durable decoration.
Sycamore, Acer pseudoplatanus, leaves are one step up in size to Hazel, but have a strong and quick colouring effect. They bleach out quite quickly and the remaining semi-transparent leaf blades will serve as a delicious snail or shrimp food. The pH reducing capability is also short lived, and after the initial sudden drop it will rise again.
The largest leaves of the domestic bunch come from the Plane tree, Platanus x hispanica, which
is another “urban warrior” that’s very tolerant of pollution. It is a perfect choice as leaf litter for
larger fish tanks, as it only has negligible influence on water colour and acidity.
Good for your fish and good for you!
Collecting leaves offers an excellent opportunity to get your partner and/or kids involved in your hobby. Who would resist an offer to visit the nearby country park or forest on a beautiful and sunny autumn day for a healthy walk? My children certainly enjoy collecting fallen leaves — they can fill up my store very quickly.
You can simply drop the required amount of dried leaves into your tank, but if you want them to sink faster you can pour boiling water over the leaves before you add them. This is also useful if you want to reduce water discolouration in your aquarium.