View Full Version : Skimmers!

Pride of the rockies
09-23-2010, 03:18 PM
I just have a question about skimmers, what kinds are there, which kinds work best, do skimmers take out anything that I wouldn't want them to (ie: trace minerals). Figured since this is the newbie portion this info would be nice to know for all of us newbies.

09-23-2010, 03:56 PM
Man, talk about a broad question...

Here's my $.02

You could classify skimmers a number of ways, but let's start here, HOB, Internal and External...

There are HOB (Hang on back) skimmers which mount directly to your display tank, one of the most commonly used and effective HOB Skimmer is the Aqua C Remora and Remora Pro. This skimmer uses injection to achieve skimmate which I will discuss later. There are Internal skimmers which are commonly used within a sump and create skimmate a number of different ways which again I will cover later. Similar to the internal skimmer is the external skimmer which work much like the internal except it does not need to sit in a body of water to function. Instead the sit under the tank, next to the tank, in another room, really anywhere you can plumb them into the system.

Downdraft Skimming:
Popular in the 80's and some of the 90's an air stone or woodblock was connected to an airline drive by a pump and placed at the bottom of a reactor tube while tank water was cycled through the reactor from top to bottom. The bubbles would travel up the reactor and through the tank water as it passed downward, creating foam at the top of the reactor much in the same way we do today.

Injection Skimming:
This method I already mentioned with the HOB Remora, can be best described by taking a garden hose, placing your thumb over the end of it and spraying this into a bucket of water. The jet of water catches pieces of air as it hits the surface of the water creating bubbles. The most common skimmer which uses this method is Aqua C. Due to the spray, they are sometimes loud to run, and require a dedicated pump to force the water through the injector.

One of the most common methods for creating bubbles is to place a venturi injector on the intake of a water pump. The water pump injects water into a skimmer reactor and with venturi in place also pulls air. The venturi restricts the amount of water allowed into the pump creating low pressure in the center. This low pressure (cavitation) allows air to pass (through an air tube) into the venturi and mix with the water and pumped directly into the skimmer body. Recent changes to the pump impeller have been replaced with needles instead of blades to chop the bubbles finer, creating more surface area to collect waste. Also know as a needlewheel skimmer.

Beckett Skimmers:
These work much like a venturi, but instead of pulling the water through a device to inject air, it forces the water though pulling in air. Due to the pressure required to drive these skimmers more aggressive and higher watt high pressure pumps are required. These pumps are typically external which prevent excess heat from being added to the water, but are louder and the injection process from the beckett is also more loud than a traditional venturi.

There are a number of different reactor bodies now available on the market from wide and short, tall and skinny, and the most popular trend is cone shaped, but they all have the same principle, and that is to inject the most amount of air into a water column allowing the air to trap waste particles and collect that foam in a cup to be removed on a regular basis.

There is much debate not only on what is the best skimmer, but also on quality of pumps, craftsmanship of the skimmer body, and easy of cleaning.

I'm not going to tell you which one is the best, as everyone has their own opinion, all I can say is find out what works for your needs, fits in your budget, and if all else fails read what others are using and how well it's performing for them.

09-23-2010, 04:38 PM
New technology in skimmers is the cone style. Older ones are just cylinders with pumps and maybe a bubble plate in them. Even older, the Aqua C with injectors.

09-23-2010, 05:44 PM
Venturi nozzles are a set of convergent and divergent nozzles (even if they don't look very convergent or divergent). As flow accelerates it creates a low pressure area in the nozzle that can draw in gas or fluid. To provide that flow you can put a venturi on the inlet or outlet of a pump. Cavitation has nothing to do with venturies or normal pump operations.

Becketts are just a fancy venturi with more air ports to the low pressure area. The difference in power use is that Becketts or Aqua Cs use a pump to push water through a nozzle. The more water you push, the more power you need. Needle wheel venturi skimmers use much less power because they are moving a combination of air and water. They move much less water. Both accomplish the same job of producing bubbles.

Becketts do a fine job and will process more water and may be a better choice with very large systems, but since both produce quality bubbles and draw lots of air, there really is no reason to get anything besides a needle wheel skimmer these days. For simplicity, ease of use, and performance needle wheels are an easy choice. There is a reason they make up a large majority of the market.

09-23-2010, 06:44 PM
Cavitation is also a result of low pressure, it was an analogy, not a method...

09-23-2010, 08:20 PM
True enough... but abnormally low inlet pressures, high temps, or insufficient flow. Not happening as a process of venturies or skimmer pumps. Just didn't want him getting the wrong idea.