Must Have: Filtration

Filtration is an important part to most tanks, unless you want to do water changes every other day.  Most people I know don’t have that kind of time.  So let’s talk about some options and the pros and cons of each.  This is by no means an absolutely comprehensive list, but it covers the most common types you will encounter at your LFS or corporate giants.

Sponge Filters

Sponge filters have been around for a very long time, and for a very good reason.  They work.  This type of filter is very easy to setup, you only need the sponge filter, some airline hose, an few bobs and bits like a check valve or splitter (if you plan on adding more sponges) and an air pump.  I usually see these being run by people with multiple tanks, because you can run as many sponges off an air pump as you have pressure to fuel them.  Basically the air causes suction, pulling water through the sponge.  This collects detritus and harmful chemicals like ammonia and nitrite.  Inside the sponge makes a great place for beneficial bacteria to camp out waiting for the all you can eat buffet to come to them.

Pros:

• Cheap:  Most filters cost around $5 or less plus the cost of an air pump (a cheap one will cost you around $8)
• Effective:  They do a great job of neutralizing harmful chemical waste and pulling in some detritus.
• Easy to Clean:  Simply rinse out the sponge in a bucket of tank water and throw it back in.
• Low Flow:  They work great for small fry, nano fish, bettas, shrimp and anything else that doesn’t like a lot of low.
• Cheap to Run:  You can run multiple filters off a single air pump.  Overall, the power consumption is relatively low.  This is great for long term savings, but also frees up your electrical outlets if you have more than one tank.  You only need one pump to run multiple tanks, so you don’t have to have additional filters plugged in for each tank.
• Access to cycled media:  You can keep multiple sponges in a tank, and then pull one out if you need to start another tank.  No waiting for anything to cycle in the new tank.  This is great if you need to start up a quick quarantine or hospital tanks.
• No spreading disease to tanks.  If you are running multiple tanks on a sump you are sharing water.  If you get ich in one tank, you’re going to get ich in all your tanks.  Sponge filters share air, no water exchange, no spreading bacteria or parasites from one tank to another.

Cons:

• Ugly:  These are not the most attractive form of filtration.  Even the higher tech looking sponges are kind of unsightly.
• They take up valuable space:  These need to be in your tank, and they do tank up a lot of real estate especially in a nano tank.
• Low Flow:  Not everything does great in low flow.  Some species do better with high flow.  I had some issues with my CO2 distributing evenly due to the low flow in the GM.

Undergravel

These have been around forever.  They have a lot of the benefits of the sponge filter, and a few draw backs all their own.  Basically its a set of plates, usually, that you put into the bottom of your tank and put gravel over it.  An air pump in the tubes in the back helps create suction that pulls crap through the gravel where it is trapped in the bottom of the tank until you vacuum it up.  I spent many hours sitting under our 50 gallon aquarium as a child telling my mom were to vacuum stuff up.

Pros:

• Cheap:  While more expensive than sponge filters, they cost between $10-$20 plus the cost of the air pump.
• Effective:  They work well because most of the detritus settles to the bottom of the tank anyway, thank you gravity, and is pulled down and locked away.
• Low Flow:  Again low flow works great for a ton of species.
• Sort of Easy to Maintain:  Just a good gravel vacuum and the filter is clean.
• Cheap to run:  Power consumption again works based on your air pump.  With a strong enough air pump, you could run multiple filters at the same time.
• Almost Invisible:  Most of the filter fits under the gravel, you only see two tubes, usually clear plastic, in the back of the filter.  So it isn’t taking up much space in your tank.

Cons:

• Moving Stuff to Vacuum:  If you have any large decor, you’ll probably need to move it once in a while to vacuum underneath it.
• Not Plant Friendly:  This will absolutely not work with most live plants.  Unless you are working with mosses, or anything that can root into driftwood, forget it.
• Low Flow:  Not all fishies like low flow.  You’ll have to add some sort of power head with the filter, that adds more cost and energy consumption.

Internal Filter

This is usually a small box that fits into the aquarium and pumps water in, over media and out the top.

Pros:

• Effective:  These work pretty well at cleaning a tank.
• Easy to Clean:  Pull out a filter and pop in a new filter.
• Adjustable Flow in some Models:  Some models will allow you adjust flow, add a spray bar or otherwise customize the way water flows back into the aquarium.  I’ve created some interesting waterfalls using this type of filter in newt tanks in the past.

Cons:

• Ugly:  No one wants to look at a big black box in their tank.
• They Take Up Space:  Just like the sponge filter, you are losing valuable real estate inside your tank.
• Expensive Cartridges:  While you can use other media than the cartridge, if you do go with the cartridge, they are pricey after a while.
• One Tank System:  This is a one shot wonder.  You need one for each tank.
• Expensive:  While not astronomical, they are more expensive than the sponge filter.  They can cost anywhere between $10 to upwards of $30+.
• Power consumption:  If you are running multiple tanks, this is especially true.
• Size Constraints:  They work well with most smaller tanks, but when you start getting above 40 gallons, your options are limited.

External/Hang on the Back Filters

Like an internal filter, only it hangs on the back of a tank.  These draw water up from the bottom of the tank via a tube through media and back out of the tank.

Pros:

• Effective:  These work pretty well at cleaning a tank.
• Easy to Clean:  Pull out a filter and pop in a new filter.
• Adjustable Flow in some Models:  Some models will allow you adjust flow.
• Available for a wide variety of tanks:  The Penguin 350 works up to 75 gallons.  Plenty of options in between.
• Space Saving:  Since it hangs on the back, it takes up almost on space in the tank.

Cons:

• Expensive:  This is the most expensive option so far.  10 gallon models are around $15, and the Penguin 350 goes up to as high as $50.  Power consumption can also be kind of high on these.
• Expensive Maintenance:  Not only is the unit pricey, but you have to pay for cartridges as well.  Unless you’re cheap like me.
• Dangerous for Some Animals:  Small fry and shrimp easily get sucked up into the intake and chopped up in the propellers.  A simple piece of sponge or netting will help this.
• Water Damage:  Occasionally these filters can overflow the box and dump water onto the floor.  This usually occurs when there isn’t enough maintenance going on and the filter becomes clogged.
• Can Burn Out/Forget to Turn On:  I’ve forgotten to turn on my filter a ton of times, or forgotten to turn it off during a water change.  If the water level drops to low, it also won’t work and will burn out your motor eventually.

Canister Filters

Canister filters are the absolute go to over 75 gallons.  These self contained pumps pull water from the aquarium through media and pump it back in.

Pro:

• Very Effective:  These are the Cadillac of filters.
• Tons of Options:  Models include extra media trays, you can customize your filtration, some even include UV bulbs to destroy algae.
• More Options:  The inlet is usually pretty straight forward, but outlet can usually be customized as well.  Either a simple dump tube, adjustable directional nozzles, even spray bars.
• Very little Real Estate:  These take up almost no room inside of the tank.  You just have the inlet and outlet to add to your tank.

Cons:

• Expensive:  They are expensive to buy, usually costing around $80 and up.  Expensive to run since they take quite a bit of power to keep them cooking.
• Bulky Equipment:  While it doesn’t take up much room in the tank, that can’t be said for outside the tank.  They are pretty bulky pieces of equipment that need to also be put into a tub so they don’t leak all over the floor.
• Water Damage:  These can leak, and when they do they can empty most of your tank on to the floor.  Yikes!
• Dangerous to some Animals:  Little guys can get sucked up into these, and chopped up.  Although I’ve heard of shrimp surviving quite well in the bottom of canister filters.
• Labor Intensive Cleaning:  So they don’t need a ton of maintenance, but when they do it can be kind of a pain.  You need to shut it down, open it up, pull out trays of media and rinse them.  Not all units are self priming, so you need to pump them a few times to get them going.  If you don’t you can burn out expensive motors, kill your bacteria and basically crash your tank.

One type of pump I’m not going to talk about is a sump.  I have zero experience with sump systems.  Generally they are for fish tanks much larger than I have ever owned, or hope to own.  I ain’t carrying a 100 gallon aquarium anywhere.  Since I know basically nothing about them, I can’t really speak to the pros and cons.  This should give you a basic breakdown of the most common types of filtration available on the market.