Practical Fishkeeping Diploma - Week 5, Day 5


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Here's the last lesson of week five of the Practical Fishkeeping Aquarist Diploma. Next week, you will be able to revise each module and take the test.

Week 5, Day 5: Cleaning

Gravel and sand needs regular cleaning, to remove food and faeces. The best way to clean gravel is with a gravel cleaning siphon, combined with a partial water change.

Sand is usually too fine to be cleaned this way. Physically rake through sand with an aquarium planting tool or (carefully) with fingers to stir up debris. When waste settles back on top of the sand, use a siphon to skim it off.

Recirculating vacuum cleaners can also be used with either sand or gravel. These lift up water and waste, returning water to the tank via a fine screen which traps debris. These vacuums can be motorised or air driven.

Water changes perform several roles, including:

Dilution of nitrate, phosphate, phenols and dyes.

Dilution of ammonia and/or nitrite during an emergency.

Replenishing essential minerals depleted by fish, plants and biological filtering.

The amount and frequency of waterchanges is linked to stocking density. A lightly stocked aquarium will deplete minerals and generate nitrate at a slower rate than a heavily stocked one.

Accurate water change volumes and frequencies require regular water tests to determine. In the event of increasing nitrates and phosphates, frequency of changes should increase. In the event of declining water hardness, water changes should be increased.

10% water changes once or twice a week are wise in tanks where fish do not tolerate fluctuations in water chemistry.

25% water changes weekly are the norm for a typically stocked aquarium.

35% water changes weekly represent the upper limit of water that can be replaced for typical community species.

50% water changes should be reserved for emergencies, such as accidental overdoses of medication, or issues like catastrophic filter failure.

Source water should be appropriate for the tank — see part one of the Diploma for details of hardness and pH. Most aquarists use tapwater, or reverse osmosis (RO) water.



Tapwater is cheap and easily accessible, but has a few drawbacks, including:

Chlorine, and possibly chloramine, added as a disinfectant.

Potential contamination with nitrates and phosphates.

Potential for very high or very low mineral content, pending its source.

Possible contamination in the event of groundworks.

RO water is a contaminant free source of aquarium water, but has drawbacks, including:

RO units for home use are expensive, and require installation into domestic plumbing.

Home RO units are wasteful (many litres of waste are generated for each litre of RO produced).

Home RO units may be damaged if pre-filters aren’t maintained.

RO water may require minerals to be added to it to make it safe to use.

Purchasing RO from a retailer requires travelling and carrying/storage of water.

RO may have low oxygen content if not aerated before use.

If using tapwater for waterchanges, it must be dechlorinated with a proprietary dechlorinator before use. Failure to do so will risk gill and skin damage to fish, compromised immune systems and potentially compromised filtration.

Dechlorinator should always be mixed with water before being added to aquaria.

Some dechlorinating devices containing carbon can be attached directly to a tap, removing chlorine as water passes through.

Replacing evaporating water in a tank should always be carried out with a mineral free source such as RO where possible. Minerals aren’t depleted with evaporating water, causing the concentration in the aquarium to increase slightly. Repeatedly topping up evaporation with mineral rich water will lead to an increased hardness level in the tank.

Testing water should take place weekly, for the water quality parameters looked at in part one of the Diploma.

Water testing methods may involve probes, or colorimetric chemicals in liquid, tablet or strip kits.

Probes may be expensive and test individual parameters, but are usually highly accurate if maintained well.

Liquid, tablet and dip tests are cheaper and more commonly used.

Colorimetric tests use reagents that change colour to identify levels of compounds being tested.

When testing it is vital that:

Water removed from the aquarium into test tubes does not get poured back in to the aquarium.

Testing takes place away from the tank to avoid accidental spillage.

Gloves and safety glasses are used with any reagents that pose a health hazard.

Test tubes are capped securely before any shaking of them occurs – fingers and thumbs are not suitable for capping as they pose both a health risk and may contaminate readings.

All test tubes are thoroughly washed, rinsed and dried after use to avoid contamination in later tests.

Filter maintenance.

Most filter media require cleaning weekly or fortnightly, pending type of media and the burden on it. Heavily stocked tanks will need more regular filter cleans than lightly stocked ones. Specific media requirements were discussed in part two of the Diploma.

As well as media, filter hoses, filter cases and filter impellers will also need cleaning.

Filter hoses should be cleaned with a proprietary pipe cleaning brush. Disconnect the hose from the tank and filter and clean it over a sink or in a bucket. Avoid using boiling water to flush the pipe, as this can cause injury.

Check hose ends for signs of perishing. Where the hose has become brittle, it may need to be chopped off the bring fresh hosing to the connections. Severely brittle hosing will need replacing.

Filter cases, especially strainers, can become clogged with debris. Remove them from the tank, and using a small brush, such as a repurposed toothbrush, thoroughly clean any slats and apertures.

Impellers need frequent cleaning to ensure they run unrestricted. Remove impellers from the impeller wells each time you perform filter maintenance to clean and inspect them. In particular, look for:

Uneven wear and tear on the impeller magnet.

‘Lines’ carved in to the magnet that indicate detritus has entered the impeller well.

Misalignment of the impeller shaft.

Cracks in the impeller magnet.

Missing vanes (blades) on top of the impeller.

Vanes that spin unimpeded on the magnet housing.

Any of the above signs require immediate correction, and warrant replacement of the impeller and shaft with immediate effect.

To clean the impeller, gently brush it with a repurposed toothbrush or similar, and rinse thoroughly.

Clean the impeller well with a cotton bud and flush it out with fresh water before replacing the impeller. Ensure the impeller can turn unrestricted before reassembling the filter.

That’s it for the course materials

Make sure you go back over and re-read any parts you’re unsure of, and watch this space for the launch of revision questions and the formal diploma questions!

Good luck!

Click here for revision questions and test

How to gain your diploma: Once all the course modules and revision pages have all been posted online, we will open a link to a website that allows you to take your free online exam. If you pass the exam, you will digitally receive your very own Fishkeeping Diploma, to show that you have successfully completed the course, and which is yours to display on the wall near your aquarium, hang in your fish house — or keep somewhere safe where you can take it out and just look at it from time to time.

Note: The Fishkeeping Diploma is not a formal or accredited qualification and should not be confused with the type of diploma presented by colleges, universities and other educational establishments.

Further reading from our sponsors

Guide to regular fish care

Guide to fish nutrition

Routine aquarium care

Feeding your fish