Biofilter calculation (m2) and flow per hour

scotty435

tiggar wrote:

Think the growbeds makes the different.

They should make a difference but part of the reason I was concerned with your phosphates and nitrates and whether you have enough plants to process the waste is that if you don't in many ways it's just like running a Recirculating Aquaculture setup. And with recirculating aquaculture you need to keep closer track of your alkalinity because that's where the inorganic carbon that the bacteria in the filters use comes from. Very low alkalinity would indicate that you are starving your filter. I also add CaCO3 but it's not always enough - usually your pH would be lower when there is a problem so it may not be a problem but other buffer systems can contribute to pH :dontknow:

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TCLynx

Another warning indicator that there is a problem is if pH is not regularly needing to be buffered up, it can indicate an anaerobic condition.

tiggar

Thanks for your help.
The hole filter contains 4m3 total volume.
The brushes are the prefilter and still smells only biologic not for anaerobic conditions.
The egg shells are as puffer for the lots of rainwater which my system gets over the year.

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coachchris

scotty435 wrote:

Each Kh unit represents around 17 mg of CaCO3 hardness. Having 50 to 150 mg of CaC03 hardness is acceptable. 100 to 150 would be better. The bacteria will use the CO2 and the carbonate hardness will fall along with the pH so you may have to keep watching it. If there isn't sufficient hardness it makes the pH swings greater and you risk a system crash because of lack of buffering as well. With AP it's a trade off because raising the alkalinity raises the pH out of the optimum range for running the system. Nate Storey has a video on YouTube about buffering and he runs with very little Carbonates - mostly adjusting pH using hydroxides.... but he's not having the troubles with filtration that you are.

I'm not sure this is going on but it's worth a look.

CoachChris seems to be having similar problems on his thread.

Yes, yes he is

Except it's been 6 weeks, my KH is now in acceptable range, as well as my PH being around 7.6-7.7, and my water looks like gin. Arggghh

tiggar- I'm sure it's in your thread, but how many totals gallons/liters is your system?

I feel your frustration. :upset:

tiggar

35m3 water
16m2 gb = 4m3
4m3 separate biofilter
38m3 permanent flow through biofilter
15/30 cycle to gb with 6.5m3/h pump

tiggar

I've from gb and amount of fish a 4m3 System but more water.
So i've to find the required flowrate per hour or day.
Can't believe that i need 35m3/h.
Maybe 5m3 just little bit more than 4m3 system needs

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TCLynx

Generally water flow through system is most closely tied to fish tank size/stocking/feeding. So while most grow beds don't need a huge amount of water flow through them to keep plants happy, the fish tank still need to have at least it's volume circulated and filtered each hour.

Sorry I don't wrap my head around cubic meter calculations very well and I don't know which number represents your fish tank.

tiggar

You're always in your ratio 1:1 fishtank to growbed but i'm nearly to 10:1

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TCLynx

I don't run a 1:1 system
But grow bed to fish tank ratios don't really have much to do with flow rates for the fish tank/bio-filter.

What type of grow beds (raft or media)? And is that ten times as much fish tank as grow bed? Or ten times as much grow bed as fish tank?

But in either case the amount of water flow through the fish tank and bio-filter per hour generally needs to be somewhere in the range of 1-4 times the fish tank volume per hour.

tiggar

Media bed with 4000l and fishtank with 35000l.
But only fish for 4000l stocked

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scotty435

How many fish do you actually have then? Size and type would be nice as well.

tiggar

Max 80kg at end of saison.
Different size from 20g to 1200g

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scotty435

On a large tank like this with a limited number of fish like you have, you won't need to turn the fish tank over as often as the rule of thumb suggests (once per hour). I can't tell you what your turnover needs to be but you might get a clue from one of the swimming pool systems here. At the current rate your turning it over about once every 10 hours - try going with continuous flow for a day or two, that would cut your turnover in half and see if your nitrites fall to zero. I think you may eventually be able to run at the current rate again but just to see if it clears the nitrites, give this a try.

For us non metric types

About 9200 US gallons of water
About 1050 gallons of grow bed and another similar sized bio-filter
About 850 gallons pumped per hour
176 lbs of fish at end of season

TCLynx

The challenge with Large volumes of water and not the full hourly turn over is that if there isn't adequate mixing/water movement, you may not be removing enough of the ammonia/nitrite from the water if there are areas that are not getting mixed/moved enough.

I have seen some ornamental pond sites that will specify turning the pond volume over once every two hours so that would recommend moving 17500liters per hour through your fish tank/bio-filter. I realize that is still a lot more pumping than the 4000 lph you feel should be enough but flow rate doesn't entirely scale based on stocking since it is the water the fish are actually living in that needs filtering, not just the minimum amount of water they could be stocked in.

TCLynx

One way that some systems may get away with not pumping as much water around the system would be to incorporate some airlift filters into the fish tank itself. This might be as simple as running some of the air you should have running in that huge volume of water into some air lifts with a filter sock filled with some neutrally buoyant bio-media to help work on some of that nitrification right in the fish water. (IF you are not having to actually lift the water above the surface level, airlifts are incredibly good for moving water around within the tank.)

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Biofilter calculation (m2) and flow per hour

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