Hi all,
Hi, Liking more and more the concept of keeping the filter purely working on biological, limiting input to ammonia and oxygen, in keeping with this wonder what your thoughts are on positioning the filter intake tube towards the top of the tank to prevent sucking up detritus / more oxygen?
I think it is a good idea, that is partially why wet and dry sumps with a weir, or surface intake, work so well, they are sending the surface layer of fully oxygenated water down to the biological filtration media.
I'm not too worried where I put the external filter intake, mainly because I have a PPI10 or PPI20 sponge on the intake and I always have lots of plants, so I can hide even quite a big sponge. What I do in larger tanks, where I have any internal filter or power-head (again with a sponge on the intake) as well as an external, is aim the flow from the internal filter at the external filters intake sponge. If it has a venturi on it even better, because air bubbles will adhere to the intake sponge.
I had quite a few years when I didn't keep fish, so when I came back to fish keeping in early noughties there was a lot of new kit. We'd been doing waste water work in the lab. and following this I was absolutely amazed that people were using their, now fashionable, external filters as syphons.
All the scientific interest was in oxygen and BOD, and systems were designed to separate solids out of the waste flow as quickly as possible, and then ensure that the liquid waste remained in constant turbulent motion to increase atmospheric oxygen diffusion and CO2 exchange. In situations where this didn't supply enough O2, systems were developed to inject oxygen into the waste (in much the same way that they use the oxygen barge on the Thames).
Against this, and at the same time, the aquarium filter manufacturers were stuffing their filters full of chemical and mechanical filtration media, and then saying having areas in the filter that were de-oxygenated was a good idea because it allowed the anaerobic breakdown of NO3. The first time I read this I really didn't believe it, and I had to read it several times before it eventually sank in, it was just so bizarre.
Once I started talking to L. number keepers (a lot of whom were much better fish keepers than I'll ever be) it quickly became apparent to me that the unexpected "symptom-less" fish deaths (usually large fish, often in the summer when there was thundery weather and all other fish in the tank absolutely fine) that they experienced were likely to be as a result of oxygen depletion, and that was why I wrote: <"
Aeration and dissolved oxygen in the aquarium">.
cheers Darrel
