Things I have learnt since starting hybrid systems.

[Kobus Jooste]

The most important thing is to abandon the single pump lay-out if you want to have media beds and rafts / NFT in a compact space.  In the past, I could drain gravel beds into rafts and then to a sump full of netting.  This kept the water in the system clear and the roots in the rafts looking good.  My new lay-out is NFT above and raft at the same height as the media beds, thus the single supply line I have been using is really too dirty for NFT.  Option 1 is in line filters, and option 2 is small secondary pumps for the NFT.  I'm going for the latter.  A high head low wattage pump will be tossed into the sump as soon as I have installed a internal configuration that settles the solids out prior to it getting to the pump.

 

The second issue I am picking up is that hybrid systems tend to have "just enough" gravel rather than surplus, which means that fines and even intermediate solids seem to stay in the system's water.  I picked this up with the sump retro-fit.  I therefore think that if you are going to run a stacked design with raised beds and lots of media-less culture, you need to find ways to settle out fines the way it is done in raft-type systems, but without discarding it.  We are therefore talking in the direction of mineralization / digestion sections in our AP systems, but not yet solids removal.

[Harold Sukhbir]

Hi Kobus,
Do you have some type of internal filter between your FT and sump?

[Kobus Jooste]

Harold: right now there is nothing.  The water from the surface of the tank flows freely into and out of the sump connectors.  The idea was not for the sump to be a filter at all at first, but now it has the floating media in.  Because of the way it is connected though, it only seem to be getting relatvely clear water (water with fines, but very little in terms of settleable solids in the fish tank.

[Harold Sukhbir]

When the 2 interconnected sumps were in use i designed a small internal filter between both of them.Water overflowed from the FT into the first sump and through the filter in the second balancing sump. I then used the filtered sump to run up to the DWC. This system worked well, in fact, much better than the swirl/net i have now. Take a look here:

[Harold Sukhbir]

And here:

[AJ Grottke]

Harold, what type of material is inside your homemade filter?

[Kobus Jooste]

That is a very nifty little pre-filter Harold, and ifit was not for the fact that I want unimpeded flow between the tank and the sump, I would seriously consider one.  The sump in my system plays a dual role of having to balance the fish tank water volume while the gravel beds are being flooded - thus the water flows in at some point and then out again.  With a pre-filter there, not only may the flow be impeded if it gets clogged, but the reversing of the flow would tend to flush the filter again, making it a bit obsolete in the way the system operated right now.

[Harold Sukhbir]

I got some used aircondition filter from a friend. The mesh is made with 1" squares with fine mesh in the middle,cut it to fit the cylinder exactly. Actually Kobus,you can put it in the FT with the flow to the sump, that way the dirty stays in the FT and only filtered stays in the sump.It actually cleans itself with the ebb and flow. Actually you can consider it to be a reverse filter of sorts.

[Harold Sukhbir]

In the month i used it i never had to clean it and the mesh being reinforced with plastic squares, which spring back when rolled, made a tight fit within the cylinder.

Harold Sukhbir said:

I got some used aircondition filter from a friend. The mesh is made with 1" squares with fine mesh in the middle,cut it to fit the cylinder exactly. Actually Kobus,you can put it in the FT with the flow to the sump, that way the dirty stays in the FT and only filtered stays in the sump.It actually cleans itself with the ebb and flow.

[Harold Sukhbir]

Kobus said:
I'm going for the latter. A high head low wattage pump will be tossed into the sump as soon as I have installed a internal configuration that settles the solids out prior to it getting to the pump.

Harold said;
How about a separate small sump out from grow beds, overflow to FT with small pump to NFT and draining also to FT?

[Kobus Jooste]

There is not enough space in the system to fit a sump in at the level below the GB outflows and above water levels in the FT.  FT and GB are close together to allow me some more overhead space for towers, thus effectively, with a sump, I can squeeze 4 levels into about 8 feet of vertical height.

[Kobus Jooste]

Some new lessons learnt. 

 

If you have relatively small beds, and you plant relatively long-lived crops such as tomato, egg plant, cucumber, pepper, butternut and passion fruit, the beds fill up with root system rather extensively and soon you have a far murkier FT than what you had running leaf crops.  I therefore have come to the conclusion that a person can take the original ratios that we worked with and double them for the GB component if you are going to have long-rotation crops dominating the media beds.  I have presently removed the raft from one of my beds and turned it into a large but temporary filter to try and remove the excess fines in the system that is not ending up in gravel any more.  I will also seriously contemplate cutting back on my fish stocking rates or adding more gravel beds outside the original system footprint. 

[Harold Sukhbir]

Hi Kobus,

Either our systems are running parallel to each other or circumstances are coincidental but im finding we arrive at the same conclusions around the same time. On the question of murky, to me it's a question mostly of preference. Some degree of fines in the water to the roots shouldn't have to be counterproductive(especially for raft crop) as i find lettuce and bak choi are growing well even with the increase in fish size(50% over ROT stocking ratios, factored in to compensate for cleaning the swirl each week).I estimate water visibility to be reduced to about 20% from original stock.

So the water may not be appealing to my eyes but the system is in good balance for now.One of the advantages of a swirl is that it allows manipulation of the water clarity and/or its nutrient levels and also a wider tolerance of stocking densities of fish.

Kobus Jooste said:

Some new lessons learnt. 

 

If you have relatively small beds, and you plant relatively long-lived crops such as tomato, egg plant, cucumber, pepper, butternut and passion fruit, the beds fill up with root system rather extensively and soon you have a far murkier FT than what you had running leaf crops.  I therefore have come to the conclusion that a person can take the original ratios that we worked with and double them for the GB component if you are going to have long-rotation crops dominating the media beds.  I have presently removed the raft from one of my beds and turned it into a large but temporary filter to try and remove the excess fines in the system that is not ending up in gravel any more.  I will also seriously contemplate cutting back on my fish stocking rates or adding more gravel beds outside the original system footprint.