The Stay at Home Fishkeeper - Weekend Maintenance Edition

If you’ve been looking longingly out the window yearning for some fresh air, then spare a thought for your fish – they live in an environment that depends on us to keep things sweet. Water changes are as much a part of the hobby as glass aquaria, so let’s look at what goes on inside the tiny world we create for our pets and how we can tweak things to make the most of maintenance.


Starting with the basics, fish pollute the water they swim in purely by living in it. Every gill beat, every feed and even in the case of some cichlids, every time they urinate as part of their display behaviour. All of this pollution has to go somewhere in the closed loop of an aquarium and this is where the nitrogen cycle comes in, unless you have a Hydra filter which removes nitrogenous waste in the first stages before it breaks down and reduces nitrate accumulation by cutting it off at source. Even these units won’t prevent bacteria colonising your system though; fish tanks are dynamic systems after all and they’ll quietly get on with things, converting lethal ammonia into noxious nitrite then less harmful nitrate.

Many of the issues faced by aquarists are due to problems with the balance between bacterial populations and fish populations and we’ve found that there are a couple of lifesaving products that can introduce bacterial reinforcements when needed. This is especially important for new systems or those facing a sudden increase in waste levels due to filter failure or the use of heavy medication. In these circumstances we’d recommend adding reinforcements and we’ve consistently seen good results from the Microbe Lift range.


You can see that in a hobby where many of the issues are literally crystal clear, water testing is the secret to understanding what’s happening at any given moment. Don’t forget that a water test is like a photograph and only records a moment in time – levels will fluctuate due to various factors such as feeding and even photosynthetic action of aquatic plants. In an established aquarium ammonia and nitrite will tend to settle at levels that are undetectable but there are conditions where this isn’t the case. We find that systems with extremely low carbonate hardness can test positive for low levels of nitrite because the filter bacteria are struggling.


Only by testing your carbonate hardness or KH along with your nitrite will a situation such as this be revealed. Note that this is one of two measures of hardness and general hardness (GH) won’t always relate to carbonate hardness. KH is also an important element in fish health and has been a bit neglected in favour of the nitrogenous waste compounds. In many situations, low KH will lead to fish losses that aren’t linked to other factors and frustrate attempts to solve the problem with medications for misdiagnosed illness. Even after the crazy days of maturation and chasing ammonia and nitrite it’s worth testing to see what’s going on and what measures need to be taken. Dip tests are popular as fast and approximate tools, they’re also used by our staff to check customers’ water due to the health and safety implications involved in using liquid reagents but for home use, we’d recommend a good liquid test kit.

Measuring your nitrates, phosphates and KH can give you the tools to tailor a maintenance schedule that fits your system and stocking levels. The first two will rise between changes in most aquaria that aren’t dominated by plants, whereas the KH will tend to fall. Depending on the quality of your source water, it may be that a regular partial change of around 25% tops up the carbonate hardness to 6dKH or above, as well as diluting nitrates and phosphates.


As well as these waste products from biological filtration, other substances build up in old aquarium water such as tannins from bogwood and leaf litter (which may be desirable) and metabolic by-products such as pheromones secreted by the fishes (which may not). As you can’t test for these, it’s sensible to use nitrate accumulation as a good measure of the rate at which your water becomes laden with undesirable compounds. If you choose to boost tannins, adding products such as dried Catappa leaves can help, as well as adding a microhabitat that many of our tropical fish are used to.


To make the most of your water changes, it’s good to remove as much solid waste as possible. Detritus accumulations break down into polluting organics as well as providing a refuge for parasites and pathogens. For all the areas you can reach, a gravel-cleaning siphon or vacuum is a very useful accessory. For those areas of the system that are less accessible, a bacterial sludge remover can be used. Whichever technique you use, we’ve found that reducing background waste levels has a dramatic effect on the health of the aquarium and its inhabitants, especially those species used to the relatively sterile conditions found in acidic natural habitats.


No conversation about water changes, nitrates and phosphates is complete without discussing tap water. In some parts of the country, agricultural run off and water authority additives make tap water an undesirable choice for fish keeping by introducing high levels of nitrate and phosphate before it even comes into contact with our pets. In these conditions, it’s wise to use an alternative such as reverse osmosis processed water or R.O. for short. As this water has been stripped of most dissolved minerals, it needs to have the essential carbonates reinstated – this can either be done in store (our staff will normally ask if you want buffer added) or by dosing with a product at home.