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Davej
29-07-2011, 03:20 PM
Flow rates

With any system there is always the dilemma as to what is the optimum flow rate.

Been playing around a bit with varying flow rates and think there may be a bit of a conflict between what’s required for mechanical filtration and what’s best for decent Bio.

With something like fluid K1 you could take the view that at a higher flow rate if it wasn’t converted in one pass it would be picked up in the next so the loss of efficiency in conversion was made up for by the frequency in passes through the filter.

But is this correct?

Dave

Gazfish
29-07-2011, 05:16 PM
Hi Dave,

I think flow rate is one of the most overlooked things when building a pond or setting filters up and I think many get confused in what it is and why it is so important.

Some think if they want a high flow then just stick a big pump on but I think they misunderstand how to correctly achieve this and it’s not just by installing a bigger pump.

Different filter systems and media work in very different ways and I know from all the testing I did when building my pond the difference is amazing. I found that you could get the mechanical right and the bio would be wrong. To fast on the mechanical means waste in the bio stages which is not good.

I also think a lot depends on the system and what’s going on and water changes and how well the system is looked after as this has a big impact on how a filter will function.

Back to your question which is a good one and you would think if it didn’t work on the first pass then it would gradually get better and better and I think this could be the case if it was only just to fats but if it was too fast a flow then I think this would have a bigger impact on the system.

I think lol

Doghouse Riley
29-07-2011, 07:06 PM
As there's all sorts of sizes and configurations of filters, I believe you can't decide on flow rates without at the same time considering "dwell time."
It isn't the same as in some systems the water will pass through the filters far more quickly than others, depending on their capacity.

For example, my filters for a 3000 gallon pool which are a simple foam and flowcore process, but most of the course solids end up in the bottom of the pump sump, hold nearly 140 gallons, so the water takes quite a while to pass through. I appreciate many filter systems will be more efficient than mine, but in any, I believe we have to give the biological process enough time to work.

I've done a quick calculation.
If my pump is pumping 5000 ltrs per hour, that's near as dammit 1,100 gallons.
So divided by my filter capacity of 140 gallons, the water will be changed 7.85 times ever hour.
So the "dwell time" would be near enough seven and a half minutes.

Davej
29-07-2011, 09:51 PM
Yes its interesting Guys, from my initial playing it does seem as though there are big advantages bio wise in increasing the dwell.

Hope to be in a position to run four similar containers at differing flow rates to see the ammonia and nitrite conversion soon, may add some meat to the bones...

Dave

Gavin
29-07-2011, 10:37 PM
Great post Dave, I'll be watching this post with interest...

Limey
30-07-2011, 05:05 AM
This has been something that has umm had me raising an eyebrow since I got back into koi keeping a year or so ago after being out for 10-12 yrs.

I was VERY sceptical about 2 things... MUCH faster pond volume turn overs and 'modern' filters like the Nexus. Reason... they are small compared to what I traditionally had been used to...

I often see turn over rates VERY fast in terms of pond volume, and on the face of it I believe this can be VERY misleading, particularly to a new keeper, if reading posts on the 'surface' and accepting the current wisdom.

What I mean by this is... it is easy to misunderstand that a very fast turn over compared to pond volume can be misleading if you don't realise where that turn over is coming from. If a keeper is running showers then there will be a MUCH higher turn over, and that may not be clear on first view... or in some cases not stated because its a general question that didn't require detail. e.g. if i asked everyone to quote their turn over I am sure there would be a wide variety of answers... without knowing how that turnover was achieved ie through what and the break down it is just a number.... nexus/chambers/streamflow/showers/skimmer[s].

Nexus recommends a range of flow rate for prime operation [believe I am right here] - BUT we are all individual... 'this flow rate you can feed this amount of food' - that can only be a general guide. How big are the fish... how many... do a lot of small fish produce more toxins than a few larger koi... how much air going in... how carefully do you keep things clean... what about flow restrictions... how do you know what the flow rate is....

The tester is, of course, water testing... does your set up take care of the toxins INCLUDING nitrate [I am being more and more convinced that nitrate is something that requires as much attention as ammonia and nitrite]. The accuracy and REAL usefulness of test 'kits' - I really believe them to be useful as a guide only, and want to replicate the kind of testing set up Davej has.

Lots of questions but no answers from me as usual heh... what Davej is doing will give some valuable clues - for me am going for a combo of old and new on pond build. Yes a lot of space for the filters - and main water movement will be via air uplift - anoxic filtration added into the uplift chamber new tech on skimmers - partly because I wanted big volume bio for longer dwell time for that elusive POM 'peace of mind' :). Nexus Showers etc have proved themselves, in the hands of the likes of Davej Gaz and Pondy etc - so what is the answer.... I am kind of in the mind that good mechanical - VERY good mechanical followed by MORE bio than you need... I am very convinced by k1 and bakki showers - I also believe in jap mat. For me... if I can get pond volume through through BIO mass once every 2 hrs I think that should be a decent starting point [?]. Extra mechanical and some bio via skimmers - eg sieve or multicyclone then nexus pod. Bakki showers on another skimmer line... but pure cost means thats a year away for me, and in my estimation will be extra to what I need for a couple of years anyway in terms of dealing with toxins. Will probably go down a 2 stage there - crystal bio as a first stop just for bank balance reasons.

Bio turn over of pond volume once every 2 hours in main filters 'SEEMS' reasonable to me... that may even be too fast in temrs of need [?]. Here is a test maybe>>>

TEST water for toxins
TURN OFF bio flow for 2 hrs
TEST water for toxins again

What has the change been? Again, this will will be impacted by number of fish... water volume... what about if test was repeated again and as soon as bio turned off the fish were fed their usual... That actually is a test I may well undertake when pond up [but futile if with a test kit methinks]. I do think tough that no 2 koi keepers results are likely to be the same but may give a 'straw man' indicator. Would there be much bio mass fall off from media in 2 hrs? Don't think so if it remained submerged [?]. The [?] are questions I am not certain of, but do think this thread very interesting and will follow closely.

I wont need to worry anyway, gonna be having anoxic in my set up as I said.... thank you Manky Sanke... REALLY opened my eyes - and have the wife on the case for the right litter :)