Everything about wood and roots in the aquarium

Frequently asked questions about roots

• Is the root of a coniferous tree suitable for an aquarium?
• Is the root of the fruit tree suitable for an aquarium?
• Does the root bought in the pet store need to be prepared?
• When will my root sink?
• Is brown water harmful to fish?

These and other questions bother many, more or less experienced, aquarists. Because there are many myths and untrue information about the properties of the tree, its toxicity, suitability or applicability in our tanks, I will try to bring this topic to our readers in this article.

Types of wood

Let’s start with the types of tree that we would like to use to arrange our aquarium:

• deciduous trees – the following species can be found in Poland: oak, beech, birch, ash, alder, hornbeam, poplar, maple, lime, willow, elm;
• fruit trees – these are also deciduous trees belonging to the family Rosaceae (Rosaceae), in Poland common species are: aronia, peach, cherry, pear, apple tree, mountain ash, hawthorn, almond, apricot, quince, plum tree, cherry;
• coniferous trees – in Poland common occur: pine, spruce, fir, larch and yew.

And how to check whether we deal with deciduous or coniferous wood. There is a simple method that requires drilling deep holes in an invisible place and sniffing shavings. Softwoods will be recognized after the resinous smell (turpentine fragrance), the fir additionally emits a vanilla scent, oak wood and black poplar give off a distinct scent of tannins – a tart-sour smell.

Definitions and parameters related to wood

What else you should know about wood before you decide to prepare it:

heartwood, non-heartwood / sapwood: almost every tree with age (different for each species) produces heartwood, that is, it loses the ability to conduct water in some of its cells. These cells are impregnated with heartwood substances: resins, gums, tannins, dyes, etc. The heartwood always appears in the oldest part of the tree, i.e. its center and extends towards the outside. The remaining part of the tree, the one that conducts water, is called sapwood. The ratio of heartwood to sapwood depends on the species of the tree. There are also several species in which the heartwood doesn’t arise at all. They are: birch, beech, hornbeam, sycamore, chestnut, common maple, alder, aspen. Heartwood has a higher density than sapwood.

chemical composition of wood: each type of tree consists of cellulose, lignin, hemicelluloses and additional substances, where the first 3 compounds make up 90-95%. Depending on the type of tree (deciduous, coniferous) the percentage share of the main compounds is different. Coniferous trees contain more cellulose and lignin in relation to deciduous trees. From the aquarist’s point of view, additional substances are important, which are more or less toxic to the inhabitants of our aquariums. These include tannic substances (occurring in all types of trees) and resins (occurring only in coniferous trees). These substances are primarily used to protect plants in the event of damage, as a result of fungi, bacteria or pests. Hazardous / toxic substances for fish are mainly: tannins and other phenolic compounds contained in deciduous wood (tannin substances), cyanogenic glycosides in fruit wood (a type of tanning substances) and resin acids, phenolic acids in coniferous wood (resins). Toxicity of these compounds lies primarily in their getting into the aquatic environment and undergoing transformations that lead to a change in the properties of this environment. Some of them dissolve in water, some do not, some are hydrolyzed, resulting in new compounds, etc.

• there are other ingredients that are dangerous for fish that trees produce for protection. An example may be taksin (toxic alkaloid produced by yew) or sambunigrin (poisonous glycoside produced by lilac).

It is also worth discussing some parameters of the tree, which are important from the point of view of the aquarist.

Belong to them: wood permeability – this is the ability of wood to absorb water. This size is strictly dependent on the density of wood – as its density increases, its ability to absorb water decreases. A low density tree (and what follows, it is of lesser weight) has more pores / voids through which water flows freely. Such a tree needs less time to completely soak – that is, sink in a shorter time.

• horntim 830

• ash 750

• beech 730

• oak 710

• elm 680

• maple 660

• birch-tree 650

• larch 600

• linden 530

• alder 530

• pine 480

• fir 450

• poplar 440
• spruce 430

wood drying time: the length of this time depends on several parameters: the type and thickness of wood, air circulation speed (the higher the air flow, the faster the wood dries), the humidity of the air and the condition of the tree surface (wood with bark dries significantly slower). Here, too, the density of wood has an influence: high density – longer drying time, because the pores / voids are smaller and the air has greater difficulties in free circulation.

durability of the wood to the factors causing its decomposition, in this case to water and fungi. Contrary to popular belief, the durability of a tree is not affected by its hardness but by: age, number of lignins (the more the wood is more durable and more resistant to fungal attack), type of tree (heartwood or non-heartwood / sapwood – the first is more durable), ambient temperature (constant is more favorable), type of environment (salt water speeds up the decomposition of wood). Durability of wood completely immersed in water:

• Very durable oak, horntim, elm, larch, pine

• Averagely durable beech, alder, spruce, fir

• Little durable birch-tree, sycamore, ash, chestnut, linden, poplar, willow

Resistance of wood to fungal attacks:

• Very durable   Oak, black locust

• Averagely durable   Fir

• Little durable   Spruce

• Non-durable   Beech, ash, poplar

Wood preparation

There is no tree that would be indifferent to the inhabitants of the aquatic environment. Each type of tree contains in its composition some toxic compounds that under the influence of water are washed away and may pose a threat if a specific concentration of this compound is exceeded. Wood preparation is aimed at disinfecting wood, neutralizing dangerous compounds to minimize their toxic effect in our aquarium. Therefore, this action is necessary for both purchased roots and those that are self-selected.

The method of preparation of wood strictly depends on its type: deciduous, coniferous, fruit and whether it is fresh (live) or dried (dead). The roots / pieces of wood / decayed branches (at various stages of decomposition) and covered in a large part with molds / fungi, etc., are not suitable for preparation.

Preparation of hardwood

The substances harmful to fish in this case are tannic substances (mainly tannins and phenolic compounds), which should be significantly minimized by proper wood preparation.

Root purchased in the store or fished out od swamp / bog / water reservoir in which it stayed for several years:

• mechanical cleaning of the root from the remains of bark or other impurities, eg with a brush, grinder, pressure washer,
• root disinfection – aims to remove potential fungi, bacteria and insects. The disinfection is carried out in a solution of water and salt (for every liter of water we pour 1 tablespoon of salt – there is no need to increase this amount, because the salt is only for disinfection, does not accelerate the removal of tanning substances from the tree), in a solution of Ethacridine lactate and water (a tablet for every 40 liters of water) or a solution of potassium permanganate and water. High temperature effectively kills fungi (die at 60°C), so we should boil root for about 30 minutes (there is no need to extend this process, because it does not affect the acceleration of root sinking, or accelerates the removal of tanning substances from the tree),
• boiling wood in water without the addition of disinfectant – also about 30 minutes (there is no need to extend this process, because it does not affect the acceleration of root sinking, or accelerates the removal of tanning substances from the tree),

• leaving the root to cool and thoroughly rinse it in water, which we add to the aquarium, e.g. during the change,
• checking if the root doesn’t color the water and whether it sinks – put it in a container with water (temperature such as in an aquarium) for a few hours. If the water is not tinted or tinted only slightly, and the root sinks without a problem, you can easily put it in the aquarium (in the second case remember the systematic 10-20% water changes until the dyeing subsides). When the root is not sinking, we load it and wait until it soaked (it gets saturated with water). When the root stains the water very much, we also leave it in a separate container, we change water every day and wait until the dyeing completely or substantially disappears.

Found a dry / dead deciduous tree root:

• decortication of wood: in this case, the bark should go down without a problem using your hands or chisel. However, if we have a problem with this activity, then we should bark wood after boiling in water (0.5h should be enough),
• root disinfection – aims to remove potential fungi, bacteria and insects. The disinfection is carried out in a solution of water and salt (for every liter of water we pour 1 tablespoon of salt – there is no need to increase this amount, because the salt is only for disinfection, does not accelerate the removal of tanning substances from the tree), in a solution of rivanol and water (a tablet for every 40 liters of water) or a solution of potassium permanganate and water. High temperature effectively kills fungi (die at 60°C), so we should boil root for about 30 minutes (there is no need to extend this process, because it does not affect the acceleration of root sinking, or accelerates the removal of tanning substances from the tree),
• boiling wood in water without the addition of disinfectant – also about 30 minutes (there is no need to extend this process, because it does not affect the acceleration of root sinking, or accelerates the removal of tanning substances from the tree),
• soaking the tree – in order to make it soaked and reduce its toxicity (substances hazardous to fish, mainly tannins and phenolic compounds, dissolve in water and with each change there is less and less of them). The wood should be loaded and we change the water daily. The length of wood soaking depends on the degree of its drying, dimensions and absorbability. The process can not be accelerated,
• thorough rinsing of the wood in water, which we add to the aquarium, e.g. during the change,
• placing the root in the aquarium.

Fresh / live deciduous wood – such wood has the highest amount of harmful substances:

• leaving wood in the natural environment (outside) or immersing it in a water reservoir / bog / swamp for the purpose of spontaneous natural process of toxicity neutralization of this wood by microorganisms, this process should last up to one year (the bigger the root the longer), the process we should stop in the summer season, after a long period of sunshine, when the tree will be dry / party dry. We can not change the process for express drying in an oven or microwave, unless it is a very small specimen,
• decortication of wood, if we have problems with this, we can boil wood in the water itself (about 30 minutes),
• root disinfection – aims to remove potential fungi, bacteria and insects. The disinfection is carried out in a solution of water and salt (for every liter of water we pour 1 tablespoon of salt – there is no need to increase this amount, because the salt is only for disinfection, does not accelerate the removal of tanning substances from the tree), in a solution of rivanol and water (a tablet for every 40 liters of water) or a solution of potassium permanganate and water. High temperature effectively kills fungi (die at 60°C), so we should boil root for about 30 minutes (there is no need to extend this process, because it does not affect the acceleration of root sinking, or accelerates the removal of tanning substances from the tree),
• boiling wood in water without the addition of disinfectant – also about 30 minutes (there is no need to extend this process, because it does not affect the acceleration of root sinking, or accelerates the removal of tanning substances from the tree),
• soaking the tree – in order to make it soaked and reduce its toxicity (substances hazardous to fish, mainly tannins and phenolic compounds, dissolve in water and with each change there is less and less of them). The wood should be loaded and we change the water daily. The length of wood soaking depends on the degree of its drying, dimensions and absorbability. The process can not be accelerated,
• thorough rinsing of the wood in water, which we add to the aquarium, e.g. during the change,
• placing the root in the aquarium.

Preparation of fruit wood

The substances harmful to fish in this case are tannin substances – cyanogenic glycosides, which are perfectly soluble in warm / hot water and are removed with it. Therefore, only large roots require earlier seasoning / drying.

Root dry / dead, which lay outside for several years and small roots / branches alive / fresh:

• decortication of wood: in this case, the bark should go down without a problem using your hands or chisel. However, if we have a problem with this activity, then we should bark wood after boiling in water (0.5h should be enough),
• root disinfection – aims to remove potential fungi, bacteria and insects. The disinfection is carried out in a solution of water and salt (for every liter of water we pour 1 tablespoon of salt – there is no need to increase this amount, because the salt is only for disinfection, does not accelerate the removal of tanning substances from the tree), in a solution of rivanol and water (a tablet for every 40 liters of water) or a solution of potassium permanganate and water. High temperature effectively kills fungi (die at 60°C), so the root should be boiled for about 30 minutes (there is no need to extend this process, because it does not affect the acceleration of root sinking),
• boiling wood in water without the addition of disinfectant – is aimed at neutralizing the disinfectant, as well as substances hazardous to fish – cyanogenic glycosides. The bath should last about 30 minutes and we should repeat it several times (each time we change water),
• immersing wood – in order to soak it. The wood should be loaded and we remember to change water (unfiltered, unventilated it will start to deteriorate). The length of wood soaking depends on the degree of its drying, dimensions and absorbability. The process can not be accelerated,
• thorough rinsing of the wood in water, which we add to the aquarium, e.g. during the change,
• placing the root in the aquarium.

Big roots fresh / alive that we can not boil:

• leaving wood in the natural environment, outdoors or immersing it in a water reservoir / bog / swamp for the purpose of spontaneous natural process of neutralizing the toxicity of this wood by microorganisms, this process should last several months (the larger the root the longer),
• decortication of wood: in this case, the bark should go down without a problem using your hands or chisel. However, if we have a problem with this activity, then we should bark wood after boiling in water (0.5h should be enough),
• root disinfection – aims to remove potential fungi, bacteria and insects. The disinfection is carried out in a solution of water and salt (for every liter of water we pour 1 tablespoon of salt – there is no need to increase this amount, because the salt is only for disinfection, does not accelerate the removal of tanning substances from the tree), in a solution of rivanol and water (a tablet for every 40 liters of water) or a solution of potassium permanganate and water. High temperature effectively kills fungi (die at 60°C), so we should pour boiling water over root and soak it for about 30 minutes (there is no need to lengthen this process, because it does not affect the acceleration of root sinking), the water should be constantly hot,
• soaking wood in boiling water (water should be constantly hot) without the addition of disinfectant – it is aimed at neutralizing the disinfectant, as well as substances hazardous to fish – cyanogenic glycosides. The bath should last about 30 minutes and we should repeat it several times (each time we change water),
• immersing the tree – in order to soak it. The wood should be loaded and we remember to change the water (unfiltered, unventilated it will start to deteriorate). The length of wood soaking depends on the degree of its drying, dimensions and absorbability. The process can not be accelerated,
• thorough rinsing of the wood in water, which we add to the aquarium, e.g. during the change,
• placing the root in the aquarium.

Preparation of softwood

In this case, the most harmful compounds for fish are resins (resin acids and their derivatives). The only species that does not have resin cords and does not produce resin cells is fir. Resins are water-insoluble compounds, so long soaking / boiling of such wood to get rid of these compounds does not make sense – their toxicity is still the same. Also, long drying does not neutralize resins completely (only volatile compounds), because they also contain non-volatile compounds (they evaporate faintly). Therefore, dry / dead tree as well as fresh / live tree should be prepared exactly in the same way, but in the second case the process will take much longer. Preparation of coniferous wood involves neutralization of resin acids with the solution of sodium hydroxide NaOH (saponification) – the reaction product will be sodium resinate, well soluble in water. Preparation steps:

• decortication – if we have a problem with this activity, then we should bark the wood after boiling in the water itself (0.5h should be enough),
• saponification of resin acids in a 2-3% aqueous solution of sodium hydroxide (NaOH), the solution should be warm (temperature 40-70°C). As a result of the reaction, soaps are created (we will recognize their formation on the slippery surface of wood, foam may be formed), which are well soluble in water,
• neutralization of hydroxide – rinse the root in warm water with a small amount of hydrochloric acid HCl (1-2% solution), it can be replaced with common citric acid,
• the saponification of resin acids and neutralization of the hydroxide are repeated until the soaping stops,
• wood should be sinking at this point, but if it’s not, we soak it in the same way as a deciduous tree,
• thoroughly rinse wood in water, which we add to the aquarium, e.g. during the change
• placing the root in the aquarium.

Using this method we should be extremely careful when in contact with chemicals and during the bath – use personal protective equipment (rubber gloves, eye protection, respiratory protection) and the entire process carry out in a well-ventilated room. Wood preparation using this method is intended for adults and responsible persons. Theoretically well-prepared softwood should not pose a threat to our fish. However, in practice, it may turn out that the saponification process was too short and the sodium hydroxide wasn’t completely neutralized. Therefore, each aquarist has to decide whether he wants to bear the risk associated with it and expose his charges.

Additional information

Large roots that do not fit in any cooking utensils should be boiled in water (with disinfectant or not) in a suitable container, eg a tub, barrel, etc.

Each root, regardless of the type of wood, undergoes gradual decomposition in the aquatic environment. As a result, a brown coating is formed on the root that soils your hands. Under suitable and favorable conditions, the wood is also attacked by various species of fungi (mostly mold) or bacteria. We should then examine the water parameters, remove the possible cause of the mold and clean the root mechanically and through reboiling it (fungi die at 60°C).

Poorly prepared root or rotten root / which is already rotting dyes water significantly, can cause spoilage of water, its unpleasant odor, fish death.

We don’t varnish the roots – every type of paint is toxic, not to mention that the varnished root will never sink, and the wet root can not be painted (the paint will not stick).