Fish tank Filters

Canister filter is external pressurized fish filter for larger aquariums, the size varies up to 400 gallons, even more. This fish tank filters operate by using hoses to supply water to the filter system and pump the clean water back to your tank. You should pay attention on distance between your fish tank and the canister filter that set up underneath your tank. Distance affects the ability of the fish filter to pump water up. Read the manuals carefully to know the maximum distance allowed.

Almost all aquarium canister filters provide 3-stage filtration (mechanical, biological and chemical). Although all brands claim to be the best at all 3 stages, I recommend to use this fish tank filter as 100% biological filtration. Why ?

In time, accumulate waste in mechanical filter - as prefilter - will slow down the water flow that brings oxygen to biological filter. Yes, it can be prevented by cleaning your canister filter regularly, but cleaning this kind of filter is not as easy as top filter or HOB filter. For hobbyists which have limited time, it can be a problem. 

The key to choose aquarium canister filter among different brands is the amount of space provided for biological media. Also compare the features and innovative ways to deal with inherent problems s.a oxygen problem when power outage.

Internal power filters are submerged inside your tank. These fish tank filters tend to be smaller than HOB filters, meaning even smaller media chambers.

I think these fish filters are suitable for small tanks only (up to 30 gallons) or it can be used as mechanical filters to supplement canister filters, although their visibility within your tank can be disadvantage.

But, nowadays advanced aquarium technology makes internal power filters more powerful, some brands using external canister filter technology (multiple filtering) and making it suitable for bigger tanks (over 60 gallon).

These fish filters are also popular for low water habitats like turtle tanks, although top filters are better choice - from capacity & easy-cleaning viewpoint.

Internal box or corner filters are very simple filters, some plastic boxes are designed to be put at aquarium corner. It rely on air pumps to move water through the filter media - s.a sponge or filter-mat - in their chambers.

I think these inexpensive fish tank filters are only suitable for baby fishes' tank, the low flow rate ensures that the fry won't be sucked up.

Sponge filters are the simplest fish tank filters. Just connect the intake tube with an air pump using aeration-hose, the air flow will push water through the sponge. This fish tank filter provides good mechanical filtration (especially for eliminating small particles) and is excellent at biological filtration, with plenty of surface area that is easy for bacteria to colonize.

In small tanks that are stocked with small fish species like tetras, sponge filters may be the only fish filter you need. They are best for fry tanks (they won't suck up the baby fishes) or can be used in quarantine / medication tanks.

You should clean the sponge regularly to make the biological functions work. Just remember to rinse the sponge gently using it's own aquarium water to keep the bacteria alive. If you are using aeration, change your simple airstone with sponge filter for biological supplementation.

Undergravel filters are classical fish tank filters and popular in the early days. These fish filters consist of a filter-plate and uplift tubes which move water slowly through the plate. They are  usually driven by air pumps with airstones. Sponge are usually put above the filter-plate as filter media, while aquarium gravel are put afterwards to keep the sponge down.

Actually, this fish tank filter is not suitable for planted tank, nutrients for water plants can't be kept in the plants' substrate. Besides, undergravel filters require regular gravel vacuuming to avoid waste to pile up. In time, these fish filters will loose efficiency and finally you have to pull them out for cleaning.

This fish tank filter is only suitable for plain tank with unheavily stocked. Avoid keeping goldfishes or other fishes that produce a lot of waste.

I found out that undergravel filters can be modified for keeping sinking-type of water turtles. Please read our Aquatic turtle supplies article for details.

Diatom filter is the best mechanical filter available. These fish tank filters provide crystal clear water, they can also improve aquarium's water conditions by removing algae, parasites, even harmful microbes. It can keep your fish healthier and promote faster healing for the sick ones.

What makes this fish filter so powerful ? The key is in the filter media called diatomaceous earth; a sediment made of the skeletons of diatoms, whose unusual pore structure can trap the smallest particles. That's why this fish tank filter can provide crystal clear water as previously mentioned.

Diatom filter is not cheap and can become clogged very quickly. This fish filter only suitable for short period usage, not continuously!. Use it if you are having problems with fish health or algae.

Fluidized bed filters are 100% biological filtration using fine grained sand as filter media. Most biological filters won't use sand since water flow can easily disrupts it, but these fish tank filters work by suspending sand in a column of water for increased surface area and contact time. It's useful for heavy bio-loads aquariums which need great surface area for bacterial bed.

Since fluidized bed filters remove oxygen from your system, you should add aeration for oxygen supply, especially in plain / fish-only tanks. Same as most external filters, these fish filters quickly build up nitrates when power failures. Some aquarists prefer them for planted aquarium, since they won't deplete CO2 that needed for aquarium plants' living and pH buffering.

They are also great for chemical filtration, known as fluidized bed reactors. Slow water flow increases contact time with the chemical media allowing highly efficient chemical filtration. 

Wet Dry filter is the best biological filter you can find. There are 2 types of these fish tank filters : canister type and sump type, but they all have the same working principles.

Canister-type moves the water within the filter in bi-directional ways, allowing for extended contact time between bacteria colonies, oxygen and toxins to be decomposed. They are very easy to install - like common canister filter - with no need for drilling in the aquarium or complicated plumbing. The fish filter is perfectly sealed so there is no risk of water overflow while gas exchange is accomplished by breathing tube. The water output follows the dynamic input - as the filter fills and empties, creating wave inside the aquarium.

Sump-type works by trickling water slowly through mechanical media, building up a good amount of oxygen before passing through the biological filter. This fish tank filter uses external reservoir of water plumbed into your tank and it's more complicated than other fish filters. It is popular and widely used -with many variations- in saltwater or reef aquariums. 

Sump-type is not suited for beginners, since it needs experience and extra efforts like good plumbing to make it works. But there are many benefits of a sump system, one of them is nitrate removal by applying algal filter within the sump. 

Sometimes, some aquarium problems come from tap water. Persistent illness, algae or chemical poisoning are some problems that can come from your tap water. No other way, you should change the source of water for your aquarium or using water purification filters.

Chemical problems. If your tap water is high in heavy metals & impurities or if you need softer water for your specific aquarium's need, you can use :

• Reverse osmosis (RO) filter. These fish tank filters remove contaminants and microscopic dissolved substances which can cause disease to your aquatic friends. These fish filters use filter media like sediment, carbon block pre-filter and membranes, it have the same working principle as drinking water's filter.

• Deionizer (DI) unit. This fish filter uses deionization cartridge to eliminate harmful elements like heavy metals and toxins. This fish tank filter can be used  alone or as an addition/combination to Reverse Osmosis (RO) filter. It will turn your tap water problem into healthy water for your tank.

• Ozonizers. These fish tank filters use ozone (O3) to oxidize pollutants, harmful elements and other contaminants. It is extremely efficient, But too much ozone can harm your aquatic friends including aquarium plants.

Micro-organisms. Your tap water can contain bacteria, fungi, viruses, protozoans, parasites and algae. It can cause illnesses to your aquatic friends. You can use :

• UV (Ultra Violet) sterilizers. These fish filters kill only free floating micro organism using high intensity ultraviolet light. It works by flowing aquarium water into UV tube where high UV light kills the microbes. It is safer than ozonizers and very easy to use. If persistent illness problems happened, you should use this fish filter after medications. It can't cure illnesses, but prevent it by purifying your tap water.

• Ozonizers. It can also kill all microbes in your tank effectively. Control the ozone level by using ozonizers with automatic controller to monitor ORP and adjust the ozone output as needed for safe and effective aquarium ozonation.

NOTE : Tank size refers to use as a primary filter.