PVA-gel beads (Polyvinyl alcohol beads) as a carbon dosing source.

Purification of aquarium water by PVA gel-immobilized photosynthetic bacteria during goldfish rearing
Journal Biotechnology and Bioprocess Engineering
Received: 5 September 2008 Accepted: 27 November 2008 Published online: 17 May 2009

http://www.springerlink.com/content/d6836368n176017q/fulltext.pdf

Abstract

This study was conducted to evaluate the ability of a PVA-gel beads filtration (PVA) system using photosynthetic bacteria to purify water. To accomplish this, duplicate long-term goldfish rearing experiments were conducted using four different types of aquarium systems (COF, PSB, EMC, and PVA). The results revealed that the concentrations of NH4 +-N on the day of a goldfish's death were significantly higher than the concentrations on other days for all the aquarium systems. In addition, the mean concentration of NH4 +-N during goldfish rearing occurred in the following order: COF system > EMC system > PSB system > PVA system. Furthermore, the mean values of all other ion concentrations (NO3 −-N, NO2 −-N, and PO4 2−-P) were found to be lowest in the PVA system. As a result, there was more prominent decomposition of organic matter in the aquarium tank containing the PVA system, as well as less turbid aquarium water and more active goldfish. Additionally, the PVA-gel beads resulted in almost complete denitrification, even after six-months of goldfish rearing. To our knowledge, this is the first study to report that PVA gel-immobilized photosynthetic bacteria have the ability to purify water. Overall, the results of this study indicate that this immobilized photosynthetic bacteria system has the potential for use as a component in circulating filtration systems.
 
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