Frequently asked questions on maintaining tank equipment


Matt Clarke answers some of the most common questions on choosing and maintaining equipment for your aquarium...

How often should I change my bulbs?

If you're growing plants or corals, you'll need to change the bulbs each year. Although they will still give off light, the light produced isn't of the same quality or spectrum as it was when the bulbs were new.

Replacing the bulbs will bring the light levels back up and allow the plants to grow properly. If you don't grow plants, there's no need to replace the bulbs until they get dimmer, flicker or fail completely.

How long should I leave the lights on for?

Leaving the lights on for too long can encourage algae to grow. If you're growing plants or corals, you ought to leave the lights on for around 12 hours each day as this is the typical amount of sunlight they'll be used to in nature.

You can get a cheap timer to plug your fluorescent lights into for about a fiver from IKEA. If you don't grow plants or corals, just switch on your lights in the evening.

The daylight from your window is adequate, you'll minimise the amount of algae you get, and save a few pounds on electricity.

Do I need a reflector?

It's advisable to add a reflector to your bulbs, otherwise much of the light emitted is absorbed by the hood. Adding a reflector could increase light levels by up to 80%.

How does a heater work?

Virtually all aquarium heaters use a bi-metallic strip thermostat to control the flow of electricity to a simple heating coil.

The strip, as the name suggests, is made from two different metals that expand and contract at different rates when the temperature changes, which causes the strip to bend away from an electrical switch inside.

When the water gets warm, the strip bends outwards and cuts off the supply of electricity, preventing the tank from getting too hot.

When the water cools, the strip contracts and closes the circuit, switching the coil on and heating the water again.

Bi-metallic strips can be capable of detecting temperature changes of about +/- 0.25C, but unfortunately, they tend to go wrong sooner or later.

And when they do go wrong, they may overheat the tank and can kill fish if you don't spot the problem quick enough.

What type of heater do you recommend?

Every brand has a few heaters that fail, but some brands seem more reliable than others. We surveyed hundreds of PFK readers last year and found that the Visitherm heaters, from Aquarium Systems, had the lowest failure rate.

They're more expensive than most, but they come with a massive five-year guarantee.

How can I stop my fish damaging themselves or my heater?

Get a heater guard. Most manufacturers make one designed to fit their heaters, but you can also get generic ones that fit most brands. This protects the heater from knocks and stops the fish leaning against it and burning their skin.

What are the benefits of an external filter?

Besides the obvious bonus of not being visible inside the tank, externals usually have much more space inside for filter media than internals do, and you can usually fill them with the media of your choice.

The extra media volume means that there's more space available for bacterial colonisation, so the filter is capable of supporting more fish (or rather more pollution) than a smaller filter, like an internal. Externals arguably need less maintenance, too.

What are self-priming externals, and why might I want one?

Externals work by drawing in water via a syphon. As such the inlet hose and canister need to be filled - and the hose must be syphoning - when you try to start up the filter or it will try to empty itself and run dry.

Self-priming externals have gadgets, like plungers and refill-inlets, to allow you to fill the body up and start the filter. Without this, you'd need to suck on the inlet or the outlet to get the filter going.

Filters without this feature are now considered a little old-fashioned.

How do I clean my external?

Switch off the mains, shut off the taps attached to the hoses and place the filter in a cat-litter tray (a clean one would be good) or an old washing-up bowl to catch spills.

Remove the sponges, or other mechanical media, and wash them in a bucket of water from the tank. If the biological media is dirty, it's worth giving this a gentle rinse, but it can usually be left untouched.

Chemical media can need monthly replacement, depending on the manufacturer's recommendations.

Never use tapwater to clean filter media - the chlorine and chloramines present will destroy the filter bacteria.

Once you've cleaned the filter, reinstall the media, connect the motor housing, turn on the taps, prime the filter and power it up.

Externals don't always start the first time, so you might need to

re-prime the filter by filling it and the inlet pipe with water to get it going again.

How do I keep my gravel clean?

Buy a gravel cleaning syphon and use it every week or so to suck out all of the dirty water within your substrate.

If done regularly, you'll have a substrate that's spotlessly clean and a lower nitrate and phosphate level, which means less algae and better-looking fish.

Personally, I've yet to find a battery-powered gravel cleaner that's as effective as a cheap, heavy-duty gravel cleaner.

I've bought a cheap tank with an undergravel filter. Is this OK?

There's nothing wrong with undergravel filters, and in many ways they are better than some internals because they've got a much bigger surface area, which means that they can support a greater number of fish.

The snag is that they need quite a bit of maintenance to work properly in the long term.

If you don't look after a tank with an undergravel, water conditions can deteriorate: the pH could drop, and the nitrate and phosphate levels could rocket.

How should I maintain my undergravel filter?

I'd suggest using a syphon-powered gravel cleaner to vacuum the substrate every week or two. If you do this regularly, you shouldn't get too many problems with the filter.

Never remove all of the substrate and wash it. By doing so, you'll kill all of the beneficial bacteria on the gravel.

How often should I replace my carbon?

Activated carbon removes certain chemicals from the water via a process called adsorption.

Activated carbon and carbon-impregnated pouches and pads have a limited lifespan of around two to eight weeks, and if left in the aquarium too long, there's a risk that they could leach chemicals back into the tank via a process called re-adsorption.

Check with the manufacturer to see how often the carbon needs to be changed as the lifespan may be linked to quality.

Why is my air pump so noisy?

Air pumps are always a little noisy, since they're vibratory. If it's suddenly got a lot noisier, it's likely the diaphragm is on its way out.

Inside the pump there's an electric coil opposite a magnet on the end of a metal bar. The back of the metal bar is attached to the top of a rubber diaphragm via a tiny screw.

When you plug the pump into the mains, the alternating current makes the magnetic field flip, causing the bar with the magnet and diaphragm attached to vibrate in-and-out quickly.

This produces the little puffs of air (and the buzzing sound) that come out of the pump. The diaphragms are made of rubber and eventually crack, causing the pump to get noisier.

To replace it, simply unplug, disassemble and fit a new one. Replacements cost a couple of quid.

What are T5s?

T5 is the name given to bulbs of 1/2" diameter. Standard fluorescent bulbs come in several diameters.

Normal 1" diameter bulbs are known as T8s, while narrower 1/2" ones are called T5s. Both have been available for years, but high-output T5 bulbs are more modern. 

Marketing hype says that they are three to four times as effective as normal T8 bulbs, last longer, run cooler, and cost less than metal halides. 

However, while the perform better than T8s, they seem to run just as hot as normal T8 fluorescents, don't appear to last as long as claimed, and cost more to use than metal halides because you need more of them (although replacement bulbs are cheaper).

However, if you've only got limited space in your hood and want to keep light-demanding plants or corals, they're a worthy step up from standard T8 bulbs.

What media can I put in my external filter?

There's an almost endless choice of media, but you really ought to have some mechanical media, such as sponges or ceramic rings, to filter out solids first. These will ensure that other media work unhindered by debris.

Biological media comes in many forms, but sintered glass media or porous minerals are quite popular. Chemical media can be added according to your needs, but most people use activated carbon or a decent phosphate remover.

How should I clean my internal filter?

Internal filters are quite basic, and bacteria-wise, you've got all of your eggs in one basket because there's usually only one sponge.

If you clean this in tapwater or replace it with a new one, you'll remove all of the bacteria required to remove pollution and your water conditions will deteriorate quickly, leading to poisoned, diseased or dead fish.

If there's only a single sponge, chop it in half. Clean one half in a bucket of old tank water when the flow rate drops, but leave the other untouched. If you need to replace the sponge because it's mis-shapen, replace one half the first month and the other the next.

This article was first published in the November 2004 issue of the Practical Fishkeeping Magazine.