The first of two problems one must solve: the water
The provision of the right water is one of the two problems for which anyone interested in these fish must have a solution. Suitable water will rarely flow directly from the water tap. Tapwater usually contains too many carbonates and bicarbonates, salts of different kinds and are much too “hard” for Parosphromenus. But even where very “soft” water flows from the tap, it is adapted to protect the sensitive water pipes by elevating the pH. We will therefore have to make provisions to get the right water.
Either a good freshwater spring close to us, or clean rainwater may be used. Because of an impact from possible air pollutants one has to be careful, but after a longer rainy period, this should be not an issue. For those dependent on their tap water. one of several, well known and industrially offered methods to bring it to the appropriate water quality must be used. These are a conductivity between about 20 and 100 micro Siemens / cm, a carbonate hardness of (almost) 0 degrees KH and a total hardness of less than 2 degrees GH. In particular, the carbonates must be removed. Therefore, some other salts (e.g. sodium chloride) may be present in a small extent.
Which method of softening the water chosen is irrelevant. Many use small reverse osmosis systems. Desalination by resins is also possible. A mixed-bed filter in which anion and cation exchange resins are mixed, is particularly convenient, since it allows a flow rate similar to that from a tap. For resin regeneration, they have to be separated from each other, which has to be done by a contract company. Today there are many, even mobile, companies, which come and bring a replacement cartridge.
The pH value should definitely be below the neutral point of 7.0, in the acidic range. In many cases, a value between 5.0 and 6.5 is suitable, however, in some ones not. Especially for wild caught fish and the species with the most delicate eggs. pH values of 4.0 and even less are often required . A water with the required low conductivity can be acidified well using acidic peat, but good results can be achieved with alder cones, and even with careful, controlled (!), dropwise addition of acidifying water additives (“oak extracts” or phosphoric acid). The biological function of these low pH values is not yet fully understood, but it is likely that it mainly is to suppress harmful bacteria which may attack the eggs of the fish. In fact, the bacterial load in highly acidic water is much lower than in less acidic or even alkaline water. Today you can buy good, easy-to-use bacteria test sets – for a friend of Parosphromenus a good acquisition.
It should not be ignored that the low pH values of natural water, in which Parosphromenus live, are mainly caused by humid acids. While there are sometimes breeding successes of Parosphromenus in plain water, usually the addition of materials that release humid substances is recommended (fresh bog wood, almond leaves soaked beech and oak leaves, alder cones).
Again, the water problem must be individually solved for each friend of Parosphromenus but whichever is chosen,it must be permanently available. However for small Parosphromenus aquariums, you need no huge quantities.
(PF)