Backyard Aquaponics
A place to discuss aquaponics

I run a 2 tank system
3 grow beds 2m x 600mm x 700mm approx.
fish tank constant height with 2 x 90 mill slo (as the height difference to the second tank is minimal.)
3 small pumps in lower tank (1 for each grow bed)
water is clean and clear in fish tank
I do it that way not because I worry about the fish being stressed to me that's illogical
but because I want my main tank to always have water in case of leaks breakages pump failure etc.
only the lower tank with yabbies and feeder fish(mossie eaters) in the lower fish tank.
and 3 pumps well why not, something will always be working with 3 pumps unless power goes off.

So for your system it’s a design thing for certain reasons, the same system with a sunken fish tank or raised grow beds can run on CF with pumping it out of the fish tank to the GB’s and the GB’s draining back to the fish tank and achieve the exact same goal without the complications of a sump


With that monster 90 000 ltr fish tank the water would fluctuate a total of 2.6 cm if the volume of the sump is taken away you could increase your FT walls from 2m to 2.026m if you wanted to maintain a certain level of your FT like a lot of people on here do


A sump is not critical for CF but if you want to design one in for your own reasons like those above do so thats the reason there are so many different systems on here

So with this type of setup is it critical to have a pump with a float switch to ensure the sump doesn't run dry, or can it be done without such a pump? I have a number of pumps already none of which have a float switch?

thanks

I'm currently running a pump with a float switch, but I couple of times it has gone to OFF when I was working on the system, but not reset once it floated, leading to the pump not starting again until I noticed it. Fortunately I keep a close eye on my system most of the time and it was only off for an hour or so in each instance. It went off because I handled it, not because of a low water level. The water has been quite low a few times, and it hasn't tripped then, so it appears to be of dubious value anyway.

For my system, I am thinking of tying the float switch up so that it is always in the ON position. I think that it is better to risk running the pump dry than to risk not having any water circulation. If your plumbing is reliable and you keep the water at a satisfactory level, the float switch becomes somewhat superfluous. If your system is unattended for long periods and the float switch is reliable, then it is a good idea.

I have a pond pump, rather than a power hungry sump pump, sitting in my sump and it is doing a fine job. It does not have a float switch attached, which was initially a concern to me. After making a few inquiries and getting some good advice on this forum I bought one with a view to fitting it at my first opportunity. For reasons that I will go into, it remains unfitted.

What I discovered with my system, and it probably applies to all systems with sumps to some degree or other, is that my pump output is largely self regulating. For instance, if for some reason less water arrives in the sump than normal, the water level will drop because the pump output is greater than the sump inflow. The sump pump output is reduced as head increases so, as the level gets lower, correspondingly less water is pumped out until an equilibrium is reached. Similarly, if more than normal water flow arrives in the sump, as the level rises the head decreases and the sump pump output increases until it matches the inflow - once again achieving an equilibrium. This has been put to the test several times in the past few months and I'm pleased to say that a new equilibrium was achieved each time, with no drama.

Obviously, this methodology involves inherent risk since the system is only self regulating within a certain range of fluctuations, albeit a decent a range, maybe as much as 15-30%. Having said that, if I had a float valve fitted then it may have caused a mini disaster just yesterday. After having a fiddle with the outlet valve on the FT and then resetting it, although it looked to be in its original position it must not have been since many hours later my attention was drawn to a louder than usual noise emanating from the sump. When I investigated I got a good look at my Jebao pump for the first time since I submerged it - it was sitting in a few cm of water, still happily pumping and feeding off the inflow water that was pouring directly onto its back. I can only assume it had been operating in this state for quite awhile. If a float switch had shut off power to the pump due to the low level, the sump would have refilled and then overflowed horribly until the flood was noticed or the FT emptied, whichever was to come first.

I suspect that the well-like shape of my sump, ie deeper than its diameter, tends to lend itself to my adapted methodology. In summary would say that it is worthwhile taking advantage of, but not relying on, this natural equilibrium trick.

thanks for the replies, I'm a little worried i'm introducing new potential issues but where I want to relocate the growbeds a sump is the only option, I'll just see if I can produce a reliable equilibrium

While it's true that you don't need a sump to run CF, it's good to get the pump away from the fish, where it can get knocked around or small fish can get sucked in. It also stops you from running the fish tank dry if a pipe gets knocked loose.

I hate to sound like a broken record but I run my system CF and I NEED a sump!

That's because you are using an existing above ground tank, Lloyd's system is different in its lay out as it has the grow beds above the fish tank level!

Either place for the sump will suit Lloyd's system, another thing for you to consider Lloyd is the future of the system, if it's going to grow quite large and take this into account when sizing your sump also if you will require an indexing valve to supply water to your system in future set it up GB/FT/sump as people have had issues with gravity fed indexing valves not having the flow for it to work properly, otherwise save yourself some digging and have it running sump/GB/FT either option works

I agree that Lloyd doesn't need to incorporate a sump, since his GBs are above the level of his FT. My headbang above was in response to what read like a general comment by scotty435 in relation to CF and sumps, rather than a Lloyd's system specific comment.

As always with any aquaponics question, the only correct answer is.... It depends.....

I'm actually relocating my growbeds from where they are now but leaving the fish tank under cover where it is, this means that my growbeds will definately be below my fish tank, this is why I now need to introduce a sump.

My fishtank at present is 1500l, however I think I will upgrade to a 3000l tank within the next year or two. I am planning on having yabbies / marron and maybe small fish in the sump, I was thinking 500l to 1000l??

In terms of pump options I have a 3000l/h and a 7000l/h however I think that I will need to downgrade from the 7000 to the 3000 with the new setup as the pump will no longer be directly feeding multiple growbeds, it'll just be a direct pipe to the fishtank.

not sure about indexing values.....

Lloyd, I think that regardless of whether your pump is feeding water to three GBs directly or returning the water that has flowed from the GBs into a sump, it is the volume of water you need to turnover and the head it has to overcome that are the critical variables to take into account. I would suggest that even without the upgrade to a larger capacity FT your pump output will be less than it is now since you will have a three tiered system instead of just two and the head is likely to be greater.

Double the volume of the FT and I think you will need your 7,000LPH pump.

yes you are right, its always trial and error for me, its good to have a range of pumps handy though

You know, this question had me wondering for days whilst reading up on all the AP FAQ's and IBC 101's how this worked in a CHIFT PIST system, and only yesterday realised what a SLO is and how it worked

The sheer amount of acronyms in aquaponics is mind-boggling but at least the uptake learning curve is helped by the process