Frequently Asked Questions

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Poret® foam related questions

Q: why use Poret® foam and not any other reticulated foam?

A: Poret® was specifically designed for aquaria and pond filtration with these main properties: Chemically resistant to bacterial degradation and hydrolysis, high compression strength to prevent shrinking, hydrophilic surface facilitates colonization by beneficial microorganisms, controlled reticulation process gives it a much greater surface than other foams, completely non-toxic.

Q: do you rinse Poret® foam before its first use?

A: yes, I recommend rinsing in quickly with tap water to remove any dust from transport.

Q: my foam smells like plastic, is this normal?

A: yes, new foam tends to foam the water a bit during the first few days and smells “foamy”; this is normal and does not impact its function nor is it in any way toxic.

Q: how often do you clean/rinse a Hamburg Mattenfilters or Cornerfilters?

A: only when needed; as long as the water goes through, just leave it alone! The longer it runs, the better it works. Mattenfilter are mimicking soil biofiltration. There are Mattenfilters in continuous operation for over 10 years! This is a low maintenance filter media, and the larger the surface area, the longer it runs without clogging. In tanks with very heavy loads, and for smaller corner filters, you can rinse it more often if needed (quarterly, biannual, or so). However, be careful not to crash the tank by cleaning the filter sheet too thoroughly.

Q: why are Poret® foam based Mattenfilters and Cornerfilters more efficient?

A:  They have a much larger volume than any comparable filter: a 20″ tall large cornerfilter is ~780 cu inch (20x13x3″), with almost 3.4 gallons of volume. Even an FX5 canister is rated by Hagen at only 1.5 gallons. The cost is less than a third of a large canister. Fewer parts, less maintenance, and all inside the tank, with no leaking risks from hoses, clamps, etc.

In a power outage, the canister will turn anaerobe and pollute the tank after about 12-15 h. A Mattenfilter or Cornerfilter can be turned off for days without any issues, which happened to me more than once with several 4-5 day power outages in Ohio on over 60 tanks.

All filters break down proteins and ammonium to nitrate and do so mostly based on the amount of food added to the tank. Filters do not make NOor NOout of thin air. Depending on the surface area filters also denitrify NOinto elementary N2 with anaerobic microorganism. It is often mentioned that happens only in deep substrate layers or live rock but that is not the complete story. Biofilms that cover any surface in the tank (and most importantly the large inner foam surface) have aerobes residing in the top layers. But in the lower layers they contain anaerobes that use the oxygen in NOfor their metabolism. The reason why the huge surface area in both Mattenfilters and Cornerfilters works so well is that the material does not clog and thus runs undisturbed for long periods of many months or even years. Hence, the biofilm becomes more mature and then breaks down more NO3. Of course, after many months or even years or with a heavy waste load, the foam like any other media needs to be rinsed to remove excess organic material to work properly.

Nitrate spikes are often the result of heavy feeding with low-quality food that is not properly digested by the fish. That quickly increases the NO3 concentration. If the filter has to be rinsed every other week or once a month because it clogs, the biofilm cannot mature fully and little denitrification is achieved.

Q: how often do you clean/rinse Poret® filter equipped canisters, hang-on-back, or other power filters?

A: this is totally dependent on the degree of waste load and clogging. Each filter and tank setting is unique. Power filters tend to have a much larger water flow compared to HMFs and their internal volume is much smaller. The smaller inflow area also means they clog more quickly. As a rule of thumb, once the flow rate drops below 50%, you should probably clean it by rinsing the foam.

Q: how do you equip various canister filters with Poret® filter foam?

A: I recommend layers of 2-in foam because that size is easy to rinse and cut to fit with large scissors or a knife. Depending on the size of the canister, start with 1-2 sheets in 10 PPI (coarse), followed by layers of 20 PPI, and finish with 30 PPI foam. You can even remove all the media baskets to put more foam into the canister to increase the filter efficiency. I do not recommend fine filter pads, filter floss, or 45 PPI foam, since these materials compact quickly and clog the filter long before there is any need to clean the bulk of the filter material. That not only shortens the maintenance intervals (more work), the cleaning also disrupts the biofilm that actually makes your filter work. All such Poret® equipped filters will be both biological as well as mechanical.

Tip: When you round off the edges to fit the sheets, reuse the leftover pieces as well, e.g. instead of ceramic tubes, since the foam has much more surface. If you bag the lose pieces into a laundry bag (so called sweater bag or similar), they are easy to remove, rinse, and then refill into the canister. Give the filter ample time (1-2 months or more) so that it builds up filter sludge. This filter sludge with its microorganisms will capture the small particles and keep your aquarium water crystal clear without the need for disposable floss or frequent filter maintenance. The foam itself can be rinsed and reused for many years.

Q: how do rinse Poret® foam sheets?

A: the easiest way is outside in the yard or driveway using a garden hose. Simply bang the sheet flat on the ground several times (Note: I recommend not wearing your best outfit doing this) to shake out the filter sludge, then rinse with the hose; repeat until the water coming out is relatively clean. Don’t overdo it! Sufficient microorganisms will survive this procedure to quickly re-establish the biology of the filter. It does not matter if you use cold or chlorine-treated water! The often repeated notion that this process would kill all the filter organisms is complete nonsense, because the residual chlorine concentration in drinking water is way too low to kill them all.

Q: how do you cut Poret® and make holes?

A: I use a very sharp large kitchen knife (smooth blade) and a dry wall ruler. Poret® is sturdy and cuts like a medium-soft cheese. First, measure and mark the size you want with a permanent marker. For Mattenfilters or sumps cut it 0.5-1.00 inch larger than the width of the space it covers. When cutting don’t squeeze it; just put the ruler on top and hold steady while you pull the knife along the ruler. For making holes just stick a pair of scissors or a pointed knife through first and then push the pipe or hose into the slit. Poret® is elastic and will give way. Drill round holes with a sharpened PVC or copper pipe.

Q: can Poret® pieces be glued together?

A: yes, using plain 100% silicone you can glue Poret® sheets together by placing 1-2 thick beads of silicone along the seam and push the pieces together tightly on a flat surface. Let the silicone cure for 24-48 h and you will not be able to separate it unless you rip the foam apart.

Q: is Poret® the same as other reticulated foams?

A: Poret® was specifically developed for biological water filtration in fresh- and saltwater as well as pond filters. As such it is free of any plasticizers (softeners), pesticides or fire retardant, which are used in most standard foams. Poret® allows the all important filter bacteria to flourish because it does not inhibit the formation of the microbial community known as biofilm. Poret® is much stronger (high compression and tear strengths) than reticulated foams to retain its shape and stay in place.

Q: what is the working principle of Poret®?

A: Poret® acts as a habitat for filter microorganisms that clean the water. Like all other filter media (with the exception of diatom filters, which are the only purely mechanical filters) the filtration efficiency of clean Poret® foam alone is really not that great. The highest efficiency is reached after several months, when some of the pore volume is filled with a flaky brown mud that smells much like moist garden soil. That mud is what cleans your water! The mud consists of more than 50% living organisms that depend on your fish waste. It is a whole zoo of little critters that form a microbial community, including aerobic bacteria and archaea that oxidize ammonia and nitrite, anaerobic bacteria and archaea that reduce nitrate, and protozoa, rotifers, and worms that consume bacteria and serve as fish food.

Q: how do you rate filtration efficiency?

A: all filter media have one thing in common; they eventually become biological filters. However, media such as filter floss or common filter foam clog readily on their surface, eventually preventing water from going through. Many – if not most – sponge filters on the market shrink after a few weeks or months in use. That happens because the outermost layer gets clogged and the low compression strength lets the foam collapse, further reducing its flow capacity. As a rule of thumb, if your sponge shrinks within the first 3-4 months of use, your are using a low compression strength foam or chose a PPI that is too fine for your flow rate. The more surface area a media provides per weight, volume, and price, the better. It should also last long and be easy to clean. Poret® has all these properties.

Q: what pore size (PPI) is best for fish fry or shrimps?

A: for tiny fish fry or shrimp I recommend the very fine 45 PPI (pores per inch) with a slow water flow through the foam so that the fry are not pulled into or against it. Air driven Poret® HMFs such as in my fishroom are best for raising fish or shrimp since the large surface area slows down the flow velocity and small fry can find little critters living on its surface as additional food.

Q: what pore size (PPI) and sheets thickness ratio do you recommend?

A: filter foam traps particles in a 3-dimensional network. But if the pores are too large the water just flows through it, or if the pores are too small, it blocks the whole sheet in the first few millimeters, rendering the rest of the thickness useless. So the thicker the foam the larger the pore size and the reverse. In general, you lose surface if the pore size increases, so you want it as fine as possible without impeding the flow. Large flow volume filtration (ponds/aquaculture) should use 10 PPI, while small filters should mostly use 20-30 PPI.

Q: can the water become foul/toxic behind the Poret® sheet in an HMF or corner filter?

A: no, since you use a power head or Jetlifter™ to pump the water back into the front of the tank there is a continuous flow much like in any other filter and no stagnant water is left in the space behind. Water in an airtight filter can become toxic only if you turn the power off, the oxygen is used up, and anaerobic processes start (hence the nasty smell). However, a 2″ or 3″ Poret® sheet in an HMF or corner filter is exposed on both side to the open, so it would take an HMF a long time to become anaerobe in the case of a power outage. A continuous 5-day power outage in September 2008 in Columbus did not harm my filters, nor the fish, after the power came back on.

Q: how do you install the lift tube in an HMF or corner filter?

A: In my experience the best result is achieved if the discharge pipe of the lift tube is about 1/2-2/3 submerged. Nesting the lift tubes in a groove of the HMF on top is the best. In addition, it provides a current along the surface that rolls down the front glass in smaller setups, which helps to move particles to the filter. Installation above the water line creates a waterfall in front of the sponge that actually moves particles away. The horizontal discharge is less noisy and messy than the simple bubble up of cube filters or similar.

Q: how much space is needed behind the Poret® sheet in an HMF or corner filter?

A: a quarter to half an inch is sufficient, but with the Jetlifter™, heater, and bulkhead my system has about 1-in of open space behind the HMF.

Q: can Poret® be used in a pond filter?

A: yes, however, keep it out of sunlight in a closed filter chamber, UV light degrades any plastic sooner or later.

Q: what PPI of Poret® is best in a sump?

A: I recommend starting with a 10 or 20 PPI sheet to trap large particles first, then follow with 30 PPI/45 PPI and perhaps Synfil as a polishing media last. The number of sheets and thickness depends on the tank and sump size, the tank inhabitants, feeding regime, etc.

Q: can Poret® be used as a pre-filter or strainer?

A: yes, 25 PPI foam cartridges fit over the usual plastic strainers on filter and sump inlets, or bulkheads. By covering the strainer with foam, fry don’t go down the drain or larger particles are not sucked into the filters and clog them prematurely.

Q: can Poret® be used in a marine (saltwater) filter or sump?

A: yes, Poret® is highly ozone, salt, and oxygen resistant, which are crucial for marine aquarium applications. However, oxidizing filtration in marine tanks is not desired because you want to remove the waste with protein skimmers before it turns into nitrate.

Q: what is Poret® made from?

A: polyether polyurethane, a highly hydrolysis-resistant plastic with outstanding aging, temperature (up to 250 °F/90 °C), and chemical stability when compared to other foams. In contrast, common polyester foams are acid and alkali sensitive. The physical properties of Poret® such as compression and tear strengths, and elongation are greater than conventional polyurethane foams. These characteristics are important because of all the chemical reactions during bacterial degradation in the filter. Poret® is also highly ozone resistant, which is crucial for marine aquarium applications.

Jetlifter™ related questions

Q: what performance do the Jetlifters™ deliver?

A: The exact water output depends on the air volume injected:

Jetlifter™ small (16 mm): 30-50 gal/h or 120-200 L/h

Jetlifter™ medium (20 mm): 50-75 gal/h or 200-300 L/h

Jetlifter™ large (25 mm): 75-125 gal/h or 300-500 L/h
(more for the longer 12″ and 16″ models but they require more air pressure.

Q: is the injector piece available for sale, so I could make my own airlifter?

A: the Jetlifter™ injectors are made to fit 16, 20, and 25 mm metric pipe, so it would not fit US customary PVC. Plus drilling some 20-30 tiny holes and deburring them is no fun.

Q: what air pumps to you recommend?

A: I prefer high quality central air pumps. Jehmco has fantastic Linear Piston Air Compressors.


Last modified: March 25, 2017 at 1:28 pm