Yet another very important aspect of fish-keeping – during a tank's initial ‘cycle' various measurements fluctuate greatly and we need to be sure it has stabilized with all the relevant readings at recommended levels.
There are numerous test kits on the market from simple ‘dip strips' to more complex ones requiring a test tube and various chemicals. Usually, these tests cause a reaction resulting in a colour change – either the colour is compared to a chart to obtain the reading or the reading from a calibrated syringe is taken as the colour changes. Some of the dip-strips test for 5 or even 6 parameters.
The obvious test in tropical tanks is the temperature – various types of thermometer are produced (stick-on LCD strips that change colour, floating/standing/stick-on in-tank thermometers or meters with a remote waterproof probe). Some tests (such as PH) can be done using special meters, where one end is dipped in the water to be tested and a digital readout produced. Whilst more expensive initially, these are more economical long-term as only occasional re-calibrating (using a calibration fluid) is required. They are also easier to interpret as colours in the other tests can be difficult to distinguish. In saltwater, refractometers or hydrometers are used to establish the salinity or specific gravity of the water. Refractometers are more expensive but more reliable whereas hydrometers using a plastic swing-arm are relatively cheap and more susceptible to error (air bubbles on the arm can cause a high reading or calcium deposits/debris the opposite). Salinity/Specific Gravity monitoring is vitally important as evaporation causes it to increase (important to top-up with RO water) and replacement water needs to be at the same levels (unless deliberately altering levels in the tank). Finally, there are computerized systems which can monitor virtually anything using probes. These systems can then be set to react depending in the reading – for example, switching heaters/fans on at set temperatures, or dosing additives. Unfortunately, these systems can be very expensive.
The following is a summary of the commonest tests done though there are many more. Most of these are vital, especially in the early stages:
Ammonia/Ammonium - NH 3 /NH 4
Nitrites - NO 2
Nitrates - NO 3
Phosphates - PO 3
General Hardness - GH
Carbonate Hardness - KH
Saltwater: As above plus:
Calcium - Ca - Tanks containing Hard corals
There are numerous other tests that can be done (for example, magnesium, strontium, iron, manganese, oxidation/redox potential(ORP) or TDS (total dissolved solids – useful for measuring the purity of your water supply), all can be important depending on the type of tank you are maintaining. Often fish, plants or corals will show symptoms indicating a deficiency of some sort – you may need to check out any number of possible causes. As you can see, this is another area that can be as involved as you wish to make it – more research?!!
The following are suggested optimum readings – some of these are guidelines only as different species thrive in different conditions: