Why lower aquarium pH?
It may not have escaped your notice that many of the fish we keep in our aquariums prefer soft, acidic water to thrive. Whilst tank-bred specimens of fish that inhabit soft and acidic waters are often happy in pH-neutral water with moderate hardness, soft, acidic water is preferable and absolutely essential for many breeding projects.
Some species are particularly insistent on soft water such as rummy-nose and cardinal tetra, or the ram cichlid. Wild-caught fish are often less able to adapt to the conditions we would like to keep them in depending on the parameters of our tapwater supplies. Whilst some of these fish can cope with moderately hard water, the liquid that pours from our taps is often immoderately so, leaving us with the task of softening tapwater and lowering its pH.
The use of natural décor to lower pH and soften the water is fairly widespread but which is the most effective item of aquarium-safe natural décor for this purpose and which ones stain the water the darkest colour? Some people prefer to keep fish in tannin-stained water as they believe that it both looks more natural and allows their fish to display better health. Others prefer clearer water such that they can view their entire aquarium setup. Either way, this experiment will enable you to make an informed decision.
Hardness and pH
Before detailing the experiment, there are a couple of things you need to understand about lowering aquarium pH and hardness: softening water and lowering its pH are not mutually exclusive undertakings: hard water acts as a buffer meaning that the addition of acidic substances may not result in a lowering of the pH. Very hard water has a large buffering capacity which explains why attempts to introduce acid through natural décor and chemicals sold for this very purpose may ultimately fail.
That said, a certain buffering capacity isn’t a bad thing as it prevents rapid decreases in pH and the subsequent stress that this can cause in fish. It suffices to say that water devoid of any buffering capacity is difficult to keep stable whilst water which is too hard is not suitable for a vast number of aquarium species. It is equally important that the water you put into your aquarium when performing a water change is a match for the water you took out to avoid causing a very rapid change in water parameters.
In order to determine which of the various products and items of natural décor are the most effective additions for lowering aquarium pH, I have devised the following experiment:
- Exactly two grams of each item is placed into a clean and clear plastic container. Measurements were made correct to the nearest one hundredth of a gram using precision scales.
- 200ml of water was added to each container, again, measured using the scales (200ml of water = 200 grams)
- The water used was RO water with total dissolved solids of 40 and a pH of 7.0.
- The pH was recorded after 48 hours and photos were taken against a white background to determine how dark the water turned. And were not placed near a heat source that could induce convection currents. The containers were not stirred during the 48 hours.
Here are the results for all of the items tested according to the method detailed above after 48 hours.
Peat Pellets: pH 5.7
Available as large or small pellets, peat pellets or granules are widely used and easy to find. They are often used to pre-filter water to be added to an aquarium as a water-softening aid. In the test, the water did not assume a brown colour and remained remarkably clear whilst also producing a drop in pH. After 48 hours, the water had a pH of 5.7.
Coco Leaves: pH 5.3
An unusual item which looks great in the tank. Coco leaves will eventually sink once fully soaked and will give an authentic impression of a rainforest floor. They do not seem to decompose as readily as Catappa leaves although they appear to lack their antibacterial properties. The water turned a golden-pink colour which was not particularly dark. The pH after 48 hours was 5.3.
Catappa leaves: pH 5.2
A firm favourite amongst aquarists, Catappa leaves are not just used for lowering aquarium pH. In addition to this role, they are also heralded for their antibacterial properties and provide food for shrimp and fry as they decompose. Some Betta fish breeders swear by their spawn-inducing capabilities. Turning the water a glorious golden colour, the Catappa leaves performed brilliantly, reducing the pH to 5.2.
Alder Cones: pH 5.8
These turned the water the darkest colour of all items tested and began leaching out tannins very quickly however the water did not see the largest drop in pH to match its colour. Alder cones may not be the most effective piece of natural décor for lowering aquarium pH, but they do make interesting additions to the aquarium. Only a few alder cones should be added to an aquarium unless you specifically wish to create an exceptionally dark tank.
Savu Pods: pH 5.3
A highly unusual object and something that has only recently become available, savu pods are great aquarium additions. They can serve as breeding caves for small species and provide a decent amount of acid too. After 48 hours, the pH had lowered to 5.3.