Unboxing and use test of the Tunze Doc Skimmer 9415

Dear readers today we are presenting to you, from the unboxing to the use test, the Tunze Doc Skimmer 9415.

The relevant skimmer is the proposal by Tunze Doc Skimmer for aquaria up to 1500 litres. As a completion to this line Tunze also offers the 9410 (recommended for aquaria up to 1000 litres) and the two older brothers 9430 and 9480 (respectively recommended for aquaria up to 3000 litres the first and 8000 litres the second).


We have tested the model provided, the Tunze Doc 9415, in an aquarium of around 300 litres sufficiently populated. The choice of the litres comes from the fact that it is not unusual to find the “advanced” hobbyist (particularly when using methods at bacterial reproduction in Total-SPS systems) tending to the purchase of an oversized skimmer that is able to guarantee a higher range of removal of nutritious sobstances obviously by safeguarding the system from an excessive impoverishment of the useful elements too. The box in which the skimmer is packaged shows on a lateral side a preview of the model with its main technical data. Once opened, let’s see what we will find on our hands…..


The skimmer is perfectly packaged and put inside a “container” in polystyrene studied and projected to the millimeter for hosting it and so that it will have no possibility of movement during the transport that may cause its accidental break. Maximum care has been addressed also to the smaller components separated from the body of the skimmer like the drain pipe, the sock-holder etc. etc., all of them are in fact individually packaged and protected with some adhesive bubble wrap. Even the skimming pump itself is inside its original box that also contains the aspiration tube and the relative accessories.


Surely the first thing we can notice are the important dimensions.

In fact Tunze declares the following size:

Length 350mm x width 300mm x height 440mm.


Below we can see all the components that we have found inside the package with the relative product codes:

9420.231 Cover of the glass:


The closing top thanks to the underlying milling fits the glasses without efforts and with very little play, in the upper part we find 3 holes for the transit of the air and the silkscreen-printed Tunze trademark.

9420.211 Scum collecting glasses:

The containment glass has a measured external diameter of 20 cm and an “internal neck” diameter of 11 cm. It is able to collect inside itself without problems up to 2 litres of product. The glass goes to saturation and therefore overflows once reached the maximum level.

Unfortunately there is not a little tube with tap for allowing the collected product to pour out in an external little tank in case of prolonged absences.

9415.241 Body of the skimmer:


Also the body of the skimmer, like the glass, has a diameter of 20 cm. Including the glass it reaches in its entirety just 44 cm. It is therefore a skimmer that really lends itself to be used also in situations where the sump has little useful space in height (considering the additional 7 cm requested for the extraction of the glass from the body of the skimmer). A fundamental point, instead giving the sizes in width, is to control in advance with attention that our sump/technical room is able to host the skimmer in its entirety.


9420.250 Disk



Output tube 150 mm



0220.500 Brush Set



9420.040 Hydrofoamer Silence

As anticipated we will find it in its original package as a completion of the skimmer.

The external submerged pump used is a Tunze 9420.04 projected for TUNZE skimmers.


Thanks to the draught of the water in sump, it directs the water and the air in the body of the skimmer.

The 9420.040 Hydrofoamer Silence is powered at 230V / 50Hz (115V / 60Hz) through a 2 m long cable with a really interesting consumption of just 15watt.

It is able to treat 1.200L\h of water with a range of 1000l\h of water.

Rotor goup of the pump: rotor with monobloc magnet at high performances, with bearing.



9410.500 Post-filter

The post filter, in black plastic like the tube and the base supporting the body of the skimmer, is needed to host its filter bag (photo a little further below).


9410.200 Bag for pst-filter

To the touch you immediately perceive how Tunze Doc Skimmer 9415 has been built in an impeccable way. All the components appear as very strong, all the details and the couplings have no imperfections.

Before starting the test we would like to talk to you about an important characteristic of this skimmer. The DOC Skimmers have a very elevated air capacity and therefore a high sensitivity to proteins, that’s how the patented system “Anti Overfoaming” is born. How does the system work? Basically it is a sort of automatic skimming.

The Anti Overfoaming system has been studied to avoid the overflow of the skimmer that can happens for example in the following cases:

  • Excessive organic charge due to the decomposition of an animal fat;
  • Aquarium just set up with living rocks;
  • Increase in the level of water on the filtering tub; supplement of liquid additives, introduction of corals etc.

The“Anti Overfoaming” system involves three functioning conditions:

(a) Normal production of scum: the scum regularly rises in the reactor, all the water levels are optimal for the maximum skimming yield.

(B) Overfoaming I: the production of scum increases due to the surface tension, the water level in the intermediate chamber rises, the water flows out from the dedicated compensation exit (2) and so extracts the air bubbles from the reactor. The quantity of scum in the reactor (3) in this way dicreases itself.

(C) Overfoaming II: the production of scum increases further, as well as the water level (1) in the intermediate chamber, entering the air circuit (4) of the Hydrofoamer: the production of bubbles in the reactor (3) is immediately stopped, the quantity of scum dicreases. Once the values of the water have improved, the skimmer starts again to function normally.

Having said that, it is finally time for the assembly.

The assembly is very easy and immediate thanks to the perfect construction of the pieces. It has to be said moreover that the skimmer arrives almost totally assembled directly from the factory. The system for grafting the glass on the body of the skimmer does not present any keeping lining or screw system. Tunze has projected this skimmer by grafting the glass on the skimming body in a totally different manner compared to the way we are normally used to. You will simply have to lean the glass on the body.

This constructive detail allows that the insertion and the remotion of the glass are very simple and without any effort (several times we have happened to necessarily “fight” with too obstinate O-Rings). The hydraulic keeping is however great and guaranteed by the precision in the construction, in fact we have not been able to note some overflows from the glass along the external body of the skimmer.

To this we have to insert the drain pipe in its place paying attention to push it until the bottom and to insert on the upper part the filter holder by letting the tube come out through it for around 1 cm.

Once this has been done we can assemble the skimming pump by screwing it in the threaded graft that we find on the body of the skimmer, this is in order to take great attention in this phase because we have to screw the pump until the end of stroke without tightening it too much, as by forcing it we could irreparably damage the plexiglass body.


All we have to do now is install the soft silicon screw tube for the aspiration of air. It is provided also as a completion for a tube tightener that will allow, with the operating skimmer, the regulation of the air flow treated by the same. This is one of the only two possible regulations in this skimmer.


Once assembled in all its parts we can put the skimmer in our technical room. The functioning is very simple. The Tunze pump will have the purpose to take water and air mixing and putting them inside the skimmer through a graft in the lower part of the same. In this way a compact scum will form (in this regard for the neophytes who read us we add that the ideal skimming can be usually obtained after some days of activity thanks to a sort of natural “degreasing”. Usually it is recommended to wash and rinse in advance the skimmers (to quicken their dosage). We have found with pleasure the presence of a post filter at the exit of the water, it can be used for the insertion of different materials like coals, resins, zeolites etc.

The only calibrations that the skimmer, as subject of the test, allows us are the the regulation of the drain and therefore the internal level and the regulation of the air aspirated.

Obviously, the more closed the drain is, the higher the internal level will be with a consequent more liquid skimming; on the contrary the more you will leave the drain open, the lower the internal level will be with a consequent drier skimming.

Once in action the skimmer is definitely silent, we have found a further attenuation using a filling material in the post filter that has, in this way, “broken” the flow of the water by filtering it.

In such conditions of use we have noticed 2 meters away from the aquarium, with open doors, a noise equal to 48 db that have further attenuated to 47 db with the doors closed.

The measurement has been made turning off all the other utilities of the aquarium that could make the measurement null.

The level in sump recommended by the mother company is between a range of 10 cm and a maximum of 20 cm. In our case the skimmer has been tested with a level of around 17 cm, with this level the skimmer worked better.

Ever since the first ignition the skimmer has immediately started to skim, also going in overskimming but immediately attenuated by Tunze’s Anti-Foaming system, and then has had a moment of inhibition like we actually expected. The running-in has not even lasted a day and the skimmer after a few hours has formed a visibly dense scum and with a good consistency, definitely “cloth-kind”. We have obtained the best regulation with the drain pipe completely inserted, the air partially closed and the level in sump, as previously said, at 17 cm. For a mono-pump, generally sensitive to the minimum variations of level, we have found it very stable and linear probably in part thanks to the ingenious “automatic” system patented by Tunze. However we recommend the insertion of this skimmer in a sump equipped with bulkhead at a constant level or, if this is not present, a great osmoregualtor (the Osmolator Tunze soon under test on these pages).

The consumption detected in use has been of 15 watt, Tunze declares 15 watt, therefore the consumption is aligned.

We have also been able to verify the discrete fair silence of the device.

We recommend this skimmer to all the users who need a mono-pump with great stability and that doesn’t need continuous regulations.

The public price is 512,50 Euro.

We thank Tunze for the provision of the object under test confident that we will be able to report to you soon our experience of use also with the other models of the DOC SKIMMER line.