Filters

Sponge or Breeder Filters

Filtering Your Aquarium Water

What Is a Sponge Filter?

Sponge filters are any aquarium filters where the aquarium water is drawn through a sponge mounted or sitting inside the fish tank. Most of the time, these filters have a replaceable sponge and are powered by an external air pump.

The sponge itself mounts to a core which, in turn, mounts to a lift tube and air line or a water pump. The sponge may rest on the bottom of the tank, in which case you can put it on, in, or under the gravel. Other models will mount to the side of the tank and should be placed as close to the bottom as they will fit to provide optimal water circulation.

How Does a Sponge Filter Work?

A sponge filter uses bubbles of air from an external air pump, or an integralwater pump to draw water through the sponge. As water is drawn out through the lift tube or pump, it is replaced by water entering the sponge. The sponge is a mechanical filter and the surface of all the bubbles or pockets in the sponge provide a bed for the bacteria of a biological filter. Sponge filters provide both mechanical and biological filtration.

What Maintenance Does a Sponge Filter Require?

The sponge will need to be rinsed or replaced every time it becomes dirty, about once every 1 to 4 weeks, depending on tank load, kind of fish, feeding schedule, type of food, cleaning schedule, and what other filtration is available and in use on the fish tank. Some sponge filters have small carbon cartridges which need to be replaced regularly - and frequently, possibly as often as daily - or can be left off entirely. Remember that carbon cartridges that become saturated with waste chemicals could potentially release other toxins into your tank.

What Should I Be Aware Of with Sponge Filters?

Most sponge filters are reasonably efficient filters for small volume tanks. These filters, especially the air driven ones, are excellent for hatcheries, maternity tanks, nursery tanks, and fry tanks, as the filter produces minimal current and has almost no way to suck the fry through the filter.

As the filter ages, the sponge will begin to deteriorate. When this happens, it is important to replace the sponge with a new one. Though these sponges may last several years or more, when they are replaced, remember you are replacing your entire biological filter unless there is another filter on the aquarium. When the biological filter is replaced, the tank will go through the cycling process again.

If you have a sponge filter in a display tank, you should consider getting a second filter so that you do not remove all of your bacteria bed every time you replace the filter sponge. Having the aquarium cycle again can be fatal to your fish due to 'new tank syndrome' and ammonia poisoning.

Remember to remove any carbon from the tank or filter before you medicate (if the carbon is working, it should remove the medication from the tank in under an hour, in which case your fish won't get treated).

Why Are Sponge Filters Sometimes Called Breeder Filters?

As mentioned at the top of the page, sponge filters are sometimes, or often, depending on which circles you are operating in and who you are listening to, referred to as breeder filters.

This is because one of the primary uses of sponge filters is by breeders in their fry tanks or nursery tanks.

These filters are used in many fish breeding operations because the filter has no way for try to get sucked into the filter and trapped or injured.

Breeders also use these filters in their rearing tanks because, short of the under gravel filter, there isn't a lower maintenance filter. And sponge filters have the advantage of being fully functional in an otherwise completely bare tank.

Because these filters can be used in completely bare tanks, sponge filters are also used by a number of fish distributors and wholesalers, where being able to quickly catch large numbers of fish is important, and where it is also important to be able to quickly see whether a tank is empty or not.

Sump Filtration

A sump filter is basically a receptacle containing media, pumps heaters etc, and in a lot of cases extra water. Sump filters can be manufactured from any basic material such as glass, acrylic or plastic. In fact, many people who use sump filters make them themselves, they are available commercially but they often cost a lot of money. Sump filters are normally used on saltwater aquariums where water quality is really very important indeed. However, people have now started using sump filters on large freshwater aquariums that contain very large fish.

Because water quality is so important in an aquatic environment, extremely efficient filtration is absolutely paramount. Even though a sump filter is quite basic and often very crudely put together, they are arguably the most efficient filtration system you can install on an aquarium. A large sump filter can contain enormous amounts of media, far more than you would ever be able to fit into a commercially available filter. So it makes sense to use a sump filter if you are intending on setting up an aquarium that may contain several hundred gallons of water.

In order to install a sump filter you must have a reciprocal which will act as your sump.  Some people start from scratch and make the sump out of the same materials that fish tanks are made from.   The simplest option is to buy a ready-made reciprocal such as a standard fish tank.  If the sump filter is going to be located under the aquarium then you will probably want to be able to see into the sump so using either a fish tank, or materials that are fish tank are made out of is probably the way to go  I myself use a cold water tank that is made from heavy duty plastic.  My sump filter is located alongside my large aquarium, a carpenter friend has cleverly concealed the ugly water tank by building around it with wood , I simply lift up a lid to gain access to the sump.

One of the first questions people ask when thinking about installing a sump filter is how big it should be.   The advantages of a sump filter is not only do they take vast quantities of media, but you also get to add some extra water to your system.  A lot of people recommend that the sump filter should be 25% the size of the main tank, I'm not sure where that came from, I've never been able to find anything official that backs this claim up.  Having said this, by the time you have installed a suitable sump, it will probably work out to be around 25% of your tank anyway, give or take a few gallons.  Of course if you want to install a really large sump filter then the only obstacle you have is space restrictions.

Whereas there's nothing stopping you putting your media, pump, heaters in one chamber, i.e. doing away with partitioning your sump filter, this really isn't very efficient, therefore it's best to create several chambers in your sump filter.  You can have as many chambers as you like, however three is probably all you really need. In order to create chambers you need to install dividers, or partitions, they are basically the same thing.  However, it's not just a case of glueing in two or three dividers, they have got to be put in properly to ensure the water can pass through the filter in the correct way.

I have made a little diagram showing the basics of how a sump filter works.  Apologies for my rather amateur drawing, I'm not an artist so this is just a basic diagram of which I hope you will be able to follow.   As you can see water enters chamber number one.  In this example the first chamber contains a mixture of biological and mechanical filtration, several hundred bio balls have been put in the chamber first, these are then topped off with several layers of mechanical sponge filtration.   The water then flows down through the mechanical and biological filtration and enters the second chamber via a gap under the divider.   Finally the water flows up through biological bio balls and over the second divider into the third chamber which contains a pump and heater in our example.  It's important to understand that if the second divider is not lower than the first divider then the water will not flow over into the third chamber, it will simply flood the whole filter.  The final chamber that contains your pump must be designed to hold plenty of water, the bigger the tank, the more water it needs to hold.

 

Let's explain a little more in detail.  The first two chambers are governed by how much water is in each, in other words if you drain the first chamber, the second chamber will also empty because they are essentially connected by that small gap under the first divider.  However, the third chamber that contains your pump is separate from the first two chambers so you could completely empty the first two chambers of water and the third chamber would not be affected at all.  When you use a sump filter it's very important that you keep a very close eye on the water contained in the last chamber. There are two extremely important reasons why a close check needs to be kept on how much water is in the last chamber.  When you switch your pump off water will continue to drain from your aquarium into the sump until the level drops just below the outlet pipe, once this happens the water will stop entering the sump from your aquarium.  When the pump is switched back on again it will start taking water from the sump, the water will continue to drop in the last chamber until the water level reaches the outlet pipe and starts to drain out back to the sump. Once this happens the water level will stop dropping in the sump filter because the water will now be circulating through the whole system.  Therefore you must always make sure you have got enough water contained in the last chamber, if you don't have enough water then you will just get to the point where the water level will drop below your pump and everything will just come to a halt. On the other hand if you have too much water in your sump filter, when you switch the pump off, you may well flood your room because there won't be enough space to accommodate the extra water that continues to flow from the tank when the pumps are switched off.  It is common practice to place a mark on the filter which indicates the lowest point at which you want your water to lay at in the sump filter.  You will also want a mark that indicates the maximum amount of water you will allow to enter that last chamber. The easiest way to fill the last chamber up to a level that is safe is to do it via the main aquarium.  So instead of putting water into the sump itself, let water drain into the sump from the aquarium, when you get to a level you are happy, you will know that it won't get any higher because when you switch the pump on, the water will drop.

One very important thing I must mention is that you mustn't submerge the very end of your outlet pipe, the part where the water comes out of and enters your tank, if you submerge it completely then you run the risk of starting a siphon when you switch the pumps off.  If this happens water will continue to siphon until the level of the water drops below these pipes, by this time you will have probably flooded your room. 

One of the problems you get when having your outlets positioned above the water is they can sometimes create quite a lot of noise, especially if you are using powerful pumps.  One way of reducing the noise dramatically is to submerge your outlets. So if you would prefer to position the outlet so it is completely submerged then to avoid creating a siphon once the pump is switched off drill a hole approximately 5 or 6 mm in the outlet pipe close to the surface.  As soon as the water level reaches the hole, air will be drawn them and it will break the syphon.  Another method which is commonly used with canister filters is to use a spray bar. Because spray bars are normally positioned just above the surface of the water, you will never experience a problem with creating a siphon when you turn your pumps off.  Spray bars are particularly effective as they can create a very good surface agitation.  You can also use spray bars to simulate rainfall which is a method that can trigger fish into spawning. If you do submerge your outlets completely then keep a very close eye on your fishes behaviour, if you see any signs of oxygen depletion then you may have to position your outlets so you are creating surface agitation. If there is quite a lot of movement on your system then hopefully plenty of oxygen is should be created, but it is something you will need to be aware of.

choosing the water pump

The water pump will circulate the water around your system, therefore you need to choose the correct pump for your sump filter. Very much like any other filter that you install and the aquarium, the pump will need to circulate the water enough times to keep the water nice and clean and free from toxins. My 300 gallon aquarium has a couple of Eheim 1262 aquarium pump

running on it, I would highly recommend these pumps, you really don't get better for your buck. These pumps are very powerful so I actually only need one of them running, the other one is purely there for backup. People often say it's impossible to have too much filtration. However, it is on the other hand possible to have a pump that is too much for your aquarium/sump. For instance, one of my pumps will circulate over 3000 gallons of water an hour. If you have two pumps running then that 6000 gallons of water an hour. Even though things will work okay, the water will be running so quickly between the sump and the aquarium, there will be an absolutely terrific amount of noise caused by all the water running through the system. So bear this in mind when choosing your pump.

When choosing your pump, have a good look at the specifications that will be listed, they will look something like below:

Pump output: 2280 l/h 502 lmp. gal./h. 602 U.S. gal./h.Delivery head: 3,10 m/wat.col. 10 ft. 2 in./wat.col.Power consumption: 50 WHose connection (suction side): Ø28mm (1")Hose connection (pressure side): Ø18mm (3/4")Dimensions: 218 x 116 x 161 8.6 x 4.6 x 6.4 in.

MEDIA

Biological media for sump filters

The biggest advantage with sump filters over normal canister type filters is they can take an enormous amount of filtration, far more than you would ever be able to get into a canister filter. I would advise you to look at the type of media that people use in outdoor pond filters. This type of media tends to be a lot bigger in diameter, therefore one bag of bio balls for instance is a lot more efficient than a box of biological media that you would buy for a canister filter. Bac bio balls are by far my favourite type of biological filtration. They come in the form of a small ball, probably slightly smaller than a ping-pong ball. They are covered in small prongs which act as a really efficient surface for bacteria to grow on. Alfagrog is another biological media which has superb bacteria holding capabilities due to its rough surface area. In fact, when I had my large sump filter I had bac bio balls into chambers, and alpha grant in another chamber. I probably had far more biological filtration that I needed, but I'd rather be safe than sorry.

Nitrate filter

A fact that not many people are aware of is a sump filter can often automatically transform itself into a nitrate filter, as well as functioning to remove ammonia and nitrite.  I know this sounds hard to believe but let me explain how this happens.  Your filtration system is not only there to remove dangerous toxins, it also removes fish poo, dirt, uneaten food and any other rubbish that you find in an aquarium.  All this nasty stuff eventually turns into a sludge that settles in the bottom of your filter.  A lot of this sludge will collect in areas of the filter that receives no water movement, when this happens anaerobic bacteria grow in the sludge as they do not require oxygen to survive.  Remember that the opposite of anaerobic is aerobic.  Aerobic organisms such as nitrifying bacteria are responsible for removing ammonia and nitrite, but these need oxygen to survive.  Now this is the really clever part, the particular anaerobic bacteria that are living in all this sludge consume nitrate, so actually all this horrible gooey mess that collects in your filter is actually working as your friend.  Now obviously there is a fine balance between how much sludge you leave in your filter, and when you have the clean it.  Actually it's not really something you have to worry about, most of this sludge that collects won't be affected by filter cleaning as it will find its way into dead areas in your sump, so you can still clean the filter without worrying about completely removing all your anaerobic bacteria.  To give you an idea of just how efficient a large sump filter can be, take a look at my 75 gallon sump filter which services my 300 gallon aquarium that contains four large adult Oscars.  I cleaned my sump for the first time in a year a few days ago.  Don't get me wrong, I have cleaned the mechanical filter sponges quite a few times as these do get clogged up, but I haven't actually emptied the sump completely.  I can hear people saying "OH MY GOD, your water must be absolutely disgusting" well, it's quite the opposite, my nitrate levels are always low, even if I leave the tank for two or three weeks without carrying out a water change.  This is purely down to the fact that my sump filter is now also functioning as a partial nitrate filter. 

It's worth mentioning that this natural phenomena will only happen in a sump filter, it will not occur in a canister filter, hob filter, under gravel or any other filter apart from a sump.  The reason being is by the time sludge builds up inside these filters, water flow is completely restricted and the filter stops functioning.  Because there is always a gap underneath your media in a sump, the sludge can build up quite happily but will almost never create a problem with restricted water flow.