Bacterial product actually works, study finds


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Many commercially available nitrifying bacterial products claim their use can make it safe to add fish to new aquarium set-ups almost immediately.

Now, for one product at least – Pond Protect-L, produced by Novozyme Biologicals Inc – such a claim may be true, according to researchers at the Virginia Polytechnic  Institute and State University.

In a study due to be published in the journal Aquacultural Engineering, the team demonstrated that Pond Protect-L was able to significantly reduce ammonia and nitrite levels during the initial maturation period of a new aquarium.

Pond Protect-L trials
The natural colonisation of a biological filter with nitrifying bacteria colony is typically quoted as taking 4 to 8 weeks, risking the exposure of any fish present to toxic levels of ammonia and nitrite.

However, trials carried out by scientists at the Virginia Polytechnic  Institute and State University on nitrifying bacterial product 'Pond Protect-L' reveal that it may help to overcome this initial hurdle.

For the trials, six identical 150-litre tanks equipped with a new biofilter – in the form of a hang-on-back filter – and a 300watt heater were set up. The tanks were filled with saltwater and 30 live White Pacific shrimp were introduced.

Three of the tanks were then treated with Pond Protect-L, while the remaining three were left untreated as a control group. Over the proceeding 28 days ammonia, nitrite and nitrate levels were monitored.

Reduced ammonia and nitrite
The team found that the ammonia and nitrite levels in the tanks treated with the Pond Protect-L never rose above 1mg/l.

Conversely, in the untreated control tanks, ammonia levels peaked at almost 3mg/l, with nitrite levels peaking ten-times higher at 30mg/l.

Furthermore, after the 28 days had elapsed nitrate levels in the treated tanks had risen from less than 1mg/l to 39mg/l, indicating that the oxidation of both ammonia and nitrite was successfully taking place within the tanks.

Meanwhile, the nitrate levels in the untreated control tanks remained below 1mg/l.

Throughout the study other water quality parameters that could have potentially affected nitrification – such as pH, alkalinity, temperature and dissolved oxygen – were also monitored on a regular basis.

Prior to their trials the team tested the Pond Protect-L product – which should be stored at 2 to 4°C – using polymerase chain reaction (PCR) techniques to confirm the presence of both ammonia- and nitrite-oxidising bacteria in the genera Nitrosomonas and Nitrobacter.

For more information, see the paper: Kuhn, DD, Dahos, DD, Marsh, L, and GJ Flick Jr. 2010. Evaluation of nitrifying bacteria product to improve nitrification efficacy in recirculating aquaculture systems. Aquacultural Engineering, doi: 10.1016/j.aquaeng.2010.07.001.