The way I see it Oase have likely sized these filters compared to the pumps such that dissolved oxygen is the limiting factor - ie. pretty much all the dissolved oxygen is being used up by the amount of biomedia present. For example the extra flow between a 600 and a 350 is enough to supply oxygen to an additional tray's worth of media under typical conditions. So, if they increased the footprint they have just made a bigger filter, that then requires a bigger pump to make use of the extra media with the associated increased running costs and increase in weight when maintenance is needed. Not necessarily a bad thing in itself, but an enlarged (in footprint) 250 or 350 is going to be a replacement for an 850 rather than one of the smaller models.
I reckon that is some good thinking! (Although I have heard that DC pumps can be slightly intolerant to sand?)
I think this is interesting and probably needs @dw1305 to opine. Oxygen exchange is (when properly set up) always taking place. i.e. surface agitation causes oxygen to come in and CO2 to go out. When you have a heavily stocked aquarium, you will have to ensure that the gas exchange meets the needs of the inhabitants - especially during the overnight period. Assuming proper gas exchanges from agitation, pumps) then the water should be 5-7ppm/l saturated with dissolved oxygen. I agree you need a stronger pump to create that turbulent flow through the filter media. However, as long as the flow of water contains, for example, 6ppm/l, then I am not sure that a massively improved pump is required to deliver oxygen to the microbes in the bio-media. You can argue that just a 3 x turnover through the filter of 6ppm/l dissolved oxygen water should be enough.
The point I was trying to make was that the bacteria in the filter consumes oxygen in the nitrification process, so water entering the filter at average dissolved oxygen levels only contains a finite amount of oxygen to be used up in the closed environment of the filter. Therefore there is a direct relationship between flow rate and effective media volume, and increasing media beyond a certain point is ineffective without a proportional increase in flow, and maybe the Oase engineers are aware of this. I am pretty sure @dw1305 has commented before that oxygen is the limiting factor in canister filters (and it would make sense that this was the case).
I think that is doable. However, as you say, it will be hard to get a good reading due to the speed and variables. However, it's a blooming good (if somewhat basic) test! I'll do this on the next water change day over the weekend.
That is it. You could have a liquid with a very high Biochemical Oxygen Demand (BOD), like <"raw sewage">, where it would be impossible to get enough oxygen into it for <"full nitrification to occur in a sealed container">.
Yes. The higher the BOD of the liquid is the <"more oxygen you need to get into the filter">, if you aren't <"pumping in extra oxygen?"> You need to increase the flow rate through the filter.
That is the problem, you can get probes that are designed to sit inside a fermentation tank etc. and measure oxygen levels, but as soon as the water leaves the filter oxygen levels will begin to rise.
I've found a paper that quantifies dissolved oxygen usage, not actually in a canister filter, but very close.
My expectations are sky-high! Don't destroy them! 😀
Yes, same here. I am glad they were realistic about the upgrades.. I think we will be waiting another five years for a true Biomaster 2 rather than a Biomaster 1.2
