Saltwater aquarium filtration for clean healthy water is one of the most important things you need for your saltwater fish and inhabitants. There are many ways this filtration can be accomplished. ROTTER TUBE replaces sump socks. No more cleaning sump socks!

ROTTER TUBES have a classy clean look: white top and bottom with your choice of color or clear.

ROTTER TUBE - Joker edition

ROTTER TUBE – Joker edition

Sump socks can be used to filter out uneaten food and fish waste. While these are excellent mechanical filtration devices, they need to be cleaned every few days and replaced after a handful of washings. They are disgusting to turn inside out and must either be sprayed down with the hose or rinsed out on rinse cycle in the washing machine a few times. I found a simpler and much easier way to filter the water coming out of your aquarium’s main overflow pvc pipe. The ROTTER TUBE was created by me, Steve Rotter, for use in saltwater aquariums in place of the disgusting sump sock. Made in USA. ORDER NOW




The ROTTER TUBE connects to your 1″ or 2″ overflow pvc pipe in your sump. The overflow pvc pipe is where the water from your aquarium drains out of. This water needs to be filtered and usually flows through a mesh or felt sump sock. Socks are usually 4″-7″ wide and 9″ long. Think of them as a felt net, where water flows through, trapping all the bad stuff in the water. These socks need to be replaced with a clean one every 3 days. You don’t want water flowing through this disgusting felt media more than 3 days. It’s bad for the fish and corals.

Instead of dealing with sump socks, the ROTTER TUBE is a bit different, while maintaining the same principal. Filtration media is placed inside the tube, which is connected directly to your main overflow. All the tank water flows through the tube and is filtered through the media provided. The ROTTER TUBE is not only really easy to clean, but lasts a very long time without need for replacement. Simply unscrew the bottom of the tube, remove media, rinse and replace. It only requires a very small piece of foam for filtration. Many people have been throwing out the foam or felt filter material and replacing with new since it is so inexpensive. We include some stiff foam felt material which can be rinsed a few times. You can use most filter media, provided you place the included tough mesh circular ROTTER disc on top of the drain to prevent clogging. Very dense and easy-flow media is included with every ROTTER TUBE. ROTTER TUBES have a classy clean look: white top and bottom with your choice of color or clear.

You can also get creative and place a bag of carbon in the tube after the filtration (recommended for the clear ROTTER TUBE, which is 3″ wide.)

ROTTER TUBE Filter available in Clear and color. Click the Order button to see all options. 


Terms in the saltwater aquarium hobby rarely have a solid concrete meaning, and a “Berlin Filtration System” is another one of those things. Basically, it is any method of filtration that utilizes a protein skimmer, liverock and should have a means for mechanical filtration as well. The system utilizes a sump, which is a tank separate from the display that contains all the equipment out of view.

Typically, the sump is located below the tank. Water from the display tank drains down through an overflow or other hole drilled into the tank, (although some people still use siphons for this – not recommended), and is aimed to pour into filter socks, or is poured over a filter pad. Utilizing gravity in this way makes mechanical filtration simple, but some of the heavier particles will remain in the tank as they sink below the drains. Stirring up these particles in your display tank by blasting your rocks with a turkey baster will help the filter remove them in between water changes.

Mechanical Filtration in your typical Berlin Filtration System –

Filter socks are usually made from a polyester blend and allow water to pass through them, but remove any particles over a certain micron size. Usually “100 micron socks” are sold in the hobby, these socks in theory will catch all particles over 100 microns, but in reality the longer they are used the less effective they will be as rushing water opens them up, and particles are broken down to sizes that will pass through the sock. Because of this, they should be taken out and cleaned each week, and depending on use and the quality of the sock, replaced when needed. You should clean the filter socks before water begins rushing over the top of them, if this happens, the sock is completely clogged, and will greatly reduce its effectiveness. To clean a filter sock, turn it inside out and spray it with a hose from the “new inside” to dislodge the particles now exposed on the outside of the inverted sock. Move back and forth, from top to bottom, before rotating the sock, continue until it is almost 100% clean. You can turn it back to its normal shape and begin using it again after it is cleaned, the hose water is very unlikely to cause any problems to your aquarium, it is too small of an amount. There are other ways of cleaning the sock, like letting them sit out in a bucket of strongly chlorinated water overnight, but I think spraying is effective for the first couple of cleanings, and then they should be replaced anyway.

Filter Pads serve the same purpose as filter socks, and are also made of a polyester blend. Filter pads contain a network of material that catches particles as water passes through the mesh. For a filter pad to work effectively, it should be situated in a way to prevent water from going around the mesh.  Usually this can be solved by placing the filter pad parallel with the floor, and allowing water to fall over the pad and then down into the sump. As long as the pad is wide and clean enough to handle the water volume falling over it, gravity will cause the water to go through the pad. Vertically aligned solutions, like the filter pad setups in hang on the back filters, care has to be taken to make sure water cannot go around the pad. In time the pad will become clogged with waste, and water will begin covering a greater area before it fall into the sump. When this happens, it is time to clean your filter pad. I like to slide a garbage bag underneath the pad before taking it outside to clean, so that a minimum amount of waste falls into the tank as the mesh is squeezed/manipulated. Arranging your filter pad for easy access in the first place isn’t a bad idea.

Both filter pads and micron socks do a good job of removing larger particles from your water, and protecting your pump from hard objects that may damage it. If you have a shortage of footprint area in your sump, micron socks are probably a better fit for you as they utilize both vertical and horizontal space as compared to filter pads that can only utilize one or the other. (Therefore you can pass more water through a finer particle trap than through a filter sock compared to a pad for the same footprint area; all other things equal).

Whether you use a filter pad or a filter sock for mechanical filtration, make sure to always turn off the return pump from the sump before cleaning them to prevent making a mess in your display tank should you make a mistake.

After water passes through the mechanical filtration area and is free of large particulates, it will usually enter the sump and be returned to the main tank, or sucked up by the protein skimmer. However, the aquarist can employ many other means of filtration in the sump.

Protein Skimmers, the Main component of the Berlin Filtration System – 

Protein skimming can get really complicated if you want to get into it, so we will stick to the basics. Protein skimmers remove organic compounds, (Dissolved Organic Compounds -“DOCs” to be more exact), that were too small to be trapped by mechanical filtration, but not have been fully broken down. They do this by utilizing a vortex chamber, that places the water in contact with air bubbles that separate hydrophobic particles from the water, such as lipids, fats and other “proteins”. (You will here the term skimming “proteins” from the water often in the hobby, even though technically your skimming more than just that). The separated particles rise in the chamber as cleaner water exits back into the sump. Eventually this film of DOCs forms into what is called skimmate, which bubbles over into the collection cup at the top of the protein skimmer. The cup should be cleaned, (with the pump that powers the skimmer turned off), weekly when the filter pads are checked, or sooner if they become full.

After water is skimmed, in the traditional Berlin Filtration System it is returned to the display tank where bacteria on and in liverock consumes ammonia, nitrite and nitrate that are a result of decay of wastes missed by the filter or caused by the tank’s bioload. However, most aquarists utilize additional filtration methods to get the most out of the sump area. Some of the more popular methods involve using water polishers, remote deep sand beds, bio-ball and/or bio-wheel areas, canister filters and refugiums. The filtration methods supplement the Berlin filtration system, and help to provide an even more balanced environment for your marine inhabitants. With filtration, the more the merrier.

Mechanical filtration operates like a very fine strainer, effective down to an almost microscopic scale; however, bacteria and protists pass through, along with all solutes. Mechanical filtration removes fine particles floating in the water, which are likely to be more objectionable to the aquarist than to the fish:  in mechanical filtration water is not “purified” in any sense.

Mechanical filtration media are fairly straightforward: most commonly, a pad or bag of close-woven synthetic fiber  is stretched over a rigid open frame to completely block the water flow. The water is forced through the medium, leaving its particulates, whether they’re silty or organic, ensnared in the web. Other mechanical filtration media besides floss include sponges, baffles such as “bio-balls” and haircurlers, etc., fused glass or ceramics, even sand grains. Temporary micro-filters using diatomaceous earth can “polish” the water to a swimming-pool clarity, when critical guests are coming over. Diatomaceous earth is a good example of a just-about purely mechanical filter.

A general hobby-supplies shop will sell you rolls of 100% polyester quilter’s batting that can be cut and used like filter floss or bonded filter pads as a much cheaper substitute medium for mechanical filtration. The batting comes in various “lofts” or thicknesses. It’s bonded with a harmless and inert cured resin that is solely meant to keep fibers from migrating. Don’t substitute cotton or cotton/poly batting: cotton will rot. If you hesitate to use a product not specifically packaged for aquarium use, get the “hypo-allergenic” polyester batting. “Hypo-allergenic” is the phrase to look for, whenever you’re looking for substitutes for captive-market aquarium goods. It means that the product is held to a high standard of freedom from chemical irritants that don’t belong in the aquarium.

In mechanical filtration, only suspended particulate matter is trapped, no matter how small those particles may be. Particulates are caught within the small spaces of the filter medium or get plastered against its increasingly sticky upstream face. Mechanical filtration operates physically, working like a sieve on a minute scale; it doesn’t affect anything that is dissolved in the water. Besides fish or snail feces, plant debris and uneaten food, particulate matter includes suspended silt (“colloids”), which can make the water hazy.

Particulates that settle out in the tank won’t get filtered. Detritus that accumulates in the upper surface of the gravel or among plant stems can be siphoned away, the prelude to a partial water change. What your siphon can’t reach you can flush into the water column with a modest jet of fresh replacement water during a water change; then the mechanical filter can take it up.

When to clean the mechanical filter. Mechanical filters clog. Fine mechanical filters clog quickly. It’s a well-worn paradox that “a dirty filter filters cleaner.” As the upstream surface of the filter clogs with particulates, a biological film of bacteria begins to form. Smaller and smaller particulate matter is trapped in the brownish sludge that develops. An ideally dirty filter is almost as effective as diatomaceous earth in polishing the water free of floating particulates. Then, at a certain point the water flow begins to be seriously impeded. Filter “by-pass” describes water flow that passes unfiltered over the top or round the sides of the filter. In an open unpressurized filter, such as the hang-on-tank (“h.o.t.”) units I favor for simplicity, you can take by-pass as a sign that the mechanical filter medium has become too clogged to function, and it’s time to rinse the filter medium— or throw it away. In an enclosed pressurized canister filter, reduced outflow is the sign to watch for.

Mechanical filter media should be gently rinsed and back-washed on a regular basis. (In my planted aquaria, where I feed a good deal of boiled spinach, I can go about a week.) But don’t be too hasty about throwing the medium away.

“Out of sight, out of mind” is a classic warning about mechanical filtration. Though the aquarium water may be clear as crystal, alas, the brown gunk developing unseen on the mechanical filter medium remains part of the recirculating system until you “export” it by cleaning the filter. Often the ammonia given off by biofilm in a dirty mechanical filter can be an underestimated source of stubborn nitrate levels in your water. Other bacteria in the filter are constantly mineralizing organic phosphate. The resulting orthophosphate can be used by algae.

Sometimes you still hear that fish swim in their own toilet. Anyone whose wholesome drinking water comes from treated and filtered river water knows this can only partly be true. All detritus in the aquarium system, wherever it may lodge, is actually in the process of being transformed. It is decomposed partly by detritivores and more thoroughly by bacteria. In the sludgelike biofilm that forms in the mechanical filter, bacteria are already working to break down the organic particulates. The “biofiltration” process is an aerobic one, which takes up oxygen and releases ammonia, carbon dioxide and dissolved organic carbon molecules. Yet when you calculate the “bioload” of the aquarium, so often you estimate the mass of your fishes, but you don’t take into consideration the high oxygen demand of that hard-working bacterial community in a dirty filter.


CLICK TO ORDER ROTTER TUBE – (2″ wide tube with 1″ pvc connection on top.)

CLICK TO ORDER ROTTER TUBE – ORIGINAL WHITE (2″ wide tube with 1″ pvc connection on top.)