Cichlids by Sanderling

Removing Surface Films From Fish Tanks

// November 1st, 2009 // Filtration, Fish Room Projects

12 hour acumulation of surface film

One of the benefits of having powerful bio-filtration system, is having the option of increasing loading densities and increasing feed rates without risk of high ammonia or nitrite levels as a result. The down side of doing this however is the accumulation of a thin film of lipo-protein and fish oils from that does not get digested by the biofilter because, being lighter than water it is unable to get to the sump. The image above shows the accumulation after 12 hours.

Its considered good practice to remove water from the bottom  of a tank as this tends to be the area of lowest oxygen concentration. The original drain design includes a spool piece that extends to the bottom of the tank and a strainer to keep young fish out of the sump. By adding a horizontal perforated piece and extending the strainer out to the center of the tank, the drain assembly also acts as a surface strainer. Below is an image of the new assembly;

 A mesh bag keeps smaller fish from a roller coaster ride to the sump and the return pump impellor;

 

Here is some video of a trial using a prototype. The extension of the horizontal piece towarrds the center of the tank effectively divides the surface of the tank in two. The film is pushed into a gyre that rotates across the front edge of the skimmer and is gradually reduced. See the videos below;

 

 

Lids were recently placed on the tanks now that the cooler weather is here in order to reduce heat and moisture loss. This has the disadvantage of reducing the amount of oxygen that can diffuse into the water at the surface. To compensate, sponge filters were added to provide some makeup air above the surface of the tank and ensure that sufficient oxygen levels a e maintained. By careful placement at the center of the gyre, the film is pushed to the outside and and against the skimmer, facilitating its constant and rapid removal;