Rena’s XP Series Filters and Snails
// October 23rd, 2009 // No Comments » // Filtration
Nitrosonomas and Nitrobacter both produce thin sticky films as they grow and divide on biomedia. These films grab organic fines from the water passing by which feed competing heterotrophic bacteria. Over time, unless actively grazed by detritovores like snails, these films become thick enough and organic rich enough that heterotrophic bacteria colonize them, and begin feeding on the trapped organic fines as well as the film itself. Because the hetertroph population can grow so much faster than the two N’s they eventually outcompete and destroy the colony by consumming most of the available oxygen.
If this happens in your filter it will be evident in milky, stringy discharges (rotting film) at start up after cleaning or if you have unplugged the filter for some other reason. Stringy discharges may be seen periodically while running as well. Generally its nothing to be overly concerned about since the heterotrophs will eventually die off and the media will be again becolonized by the two N’s.
What it indicates is that the media is not optimized for nitrification and your system would benefit from a mechanical prefilter to reduce the amount of suspended organic material channeling through the filter and fouling the thin film created by the two N’s. You can use fine pore filter media but this will tend to clog up and reduce the flow rate through the filter which can cause other problems, including oxygen depletion and general lack of performance. Alternatively you can use snails to clean the bacteria film!
When using canister filters I prefer the Rena Filstar series due to the quiet and powerful pump and the roomy media baskets. I fill them up with Fluval Prefilter media which is open enough to allow small snails complete access to maintain the bacterial film by actively grazing upon it. The impellor crushes a few up ocaisionally and sends them back to tank as fresh food for the fish.
When I clean these filters out annually, I always make sure to toss a few adult snails back into the filter before putting the lid on. I don’t run with the filter pads, but still have low turbidity in my tanks.
The ability to house snails for this synergistic biofiltration aproach is what sets the XP series of filters apart from the rest of the cannister herd in my humble opinion.
