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Hello, so, in a CHOP Mark2 kind of system, for a 55gal drum barrel fish tank, what would you experienced people recommend? As far as I understand the whole idea of the SLO is to move bottom solids away from the fish by suction, and that suction down the escape tube depends on the inbound flow rate from the pump. In my case I have an Active Aqua 400GPH pump, but there is a 1000GPH thing shipped my way soon to arrive :sneaky:

Would 1 inch plumbing do the job? Or would you use 1 1/2 inches? Here is my setup to illustrate

The weaker the flow rate, the narrower the SLO pipe should be?


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Hi José

'First order the 1" seems to do the job - but you'll also need to consider ease of maintenance

Note the outlet is gravity feed and the outlet must be able to handle the inflow - else you'll need an overflow return line (good precaution)


Flow in Qin g/h 300   from pump Q-head graph - head: - 2m
m^3/h 1.02
Flow out Qout m^3/h 7.840036 > Qin
Pipe diameter D m 0.0225
effective height h m 1.5
gravity acc g m/s^2 10
time conversion t s/hr 3600
Potensial energy Ep m.g.h
Kinetic Energy Ev 1/2.m.v^2
Pipe Area A pi.(D/2)^2
Flow velocity v sqrt (2gh)   for Ep=Ek
Flow Out Qout t.A.v

Pieter, I have decided to use  1" thinwall tubing, and as you said, if the water pressure into the fish tank is greater than what the outlet can handle, then the return line in the sump tank will have to kick in. I don't really see what would be the use of an enormous width for the SLO, other than allow the incoming water flow to exit fast enough to avoid the fish tank to overflow in unwanted ways. I think as long as there is enough pressure to fill up the outlet, the solids will move out effectively. The return line is important to help balance the pressure through the subsystems (fish tank, growbeds and sump tank).

Now, I don't know how to read those numbers. Are those in a table format? what  are the "Q"s?

Hi Jose -

I don't think the CHOP2 System is under pressure - you should rather think about constant volume flow - thus the inflow and outflow should equal for a said time period. You'll also T-off some of your flow to your grow beds - so the 300gph I've used will probably be more like 200gph -

You can ignore the figures - I just wanted to check it the outflow (Qout) can handle the inflow (Qin) - according to the model your ouput could handle about 8x your input. BUT:-

It is not a very good model as it ignores pipe friction (larger diameter pipes has less) as well as build up of residue (for larger diameter pipes the effect of build up is less). So - in short - you probably need to experiment a bit as most systems differ due to layout restrictions.  Slow bends is better than right angles and so.

I've had issues with clogging in my experimental setup - residue build up, earthworm colonies, etc -  so be prepared to be 'flexible'.


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