An improved system for the control of dissolved oxygen in freshwater aquaria

A system for the removal and control of dissolved oxygen (DO) from freshwater was designed and constructed with aquarium-type fish studies in mind. Degassed water was obtained using a partial vacuum of -14 psi, and DO regulated at an aquarium scale using electronically controlled aeration with timed partial water renewal. The degassing system was capable of producing water with ~1.7 mg L^(-1) DO within 10 min of operation, and 0.55 mg L^(-1) after 2 h. The control system was capable of maintaining DO levels of ca 0.8 mg L^(-1) over 48 h in the absence of aeration and further capable of precisely controlling DO levels as low as 1.16±0.002 mg L^(-1) (mean±SEM) with aeration over a 48 h period.