First greenhouse-scale AP - help me check for faults before I make them!

[Louise]

Finally! I have a 10 square metre (100 sq. ft.) greenhouse, and today it took its first steps towards becoming an aquaponic greenhouse.

There is a photo attached.

The setup is planned to be a CHIFT PIST but with an added deep water bed for growing duckweed. Like this:

The IBC tank is cut down so it will hold just under 800 litres (200 gal). This will be the fish tank.

That will have an overflow that fills the growbed using gravity. On the photo the growbed is the colourful thing that is obviously not a growbed just yet, but is set up to show its size. It is 2 metres long, and will hold 300 litres of media/water. I'll build a siphon to drain it into the sump tank. (Worrisome, as I never managed to make a good siphon in my indoor system.) Loop siphon - is that a good idea?

The sump tank is a blue barrel on the side, that I will have to partly submerge to get the grow bed lower than the fish tank overflow. This holds approximately 200 litres. I'm a bit concerned this might not be big enough. I don't know how much water will fit in my grow bed once it's filled with media - and the sump tank has to be able to hold it all, right? I have an alternative, a 300 litre aquarium that leaks maybe a cup per week or so, not much, but it's heavy, and I'd prefer not to use it. Anyone have a guess how much water I need to calculate for if the grow bed volume is 300 litres? Depending on the media, I suppose, I plan to use LECA (Hydroton).

From the sump tank, I'll have a pump. I thought that when I want to add another growbed along the other side of the greenhouse, that'll have to have a separate sump tank. Maybe it's good to have a pump that isn't submerged, but can suck via hoses from both sumps - is this a good idea? Will it be a problem if one sump is emptied before the other? How do I safeguard against the pump running dry? What's the advantage of a submersible pump?

The water will be pumped into the cut-off IBC top bit that sits on top of the fish tank. There I intend to grow duckweed, and just have an overflow standpipe that drains excess water into the fish tank.

This way I haven't designed in any extra aeration - where would I put that?

[Ian Cameron]

Well, lots of questions! While not an expert by any stretch of (my) imagination, there are some answers that come to mind.

1. How much water in your GB? Well, I figured about 40 -50% of total bed volume. That came very close for me using Hydroton.

2. Separate sump for additional GB. Why not plumb to the existing sump? Unless you plan on pumping back.

3. Pumps- submerged or not? I've had good results from both. But I prefer submerged. Less plumbing, and I believe it keeps pump running cooler.

4. Aeration? Absolutely. I have 2*12" air stones in each 75 gal GB, same in the 4*4 DWR, and 2 in the FT. Air is the cheapest way of promoting good growth in all aspects of my system. Also, on every water outlet I made a veturi setup to suck air in as water is passing by. Works like a charm. Fish are happy, plants are happy and I am happy:)

Hope this helps a little

[Louise]

1: Wonderful, then my barrel will be big enough!

2: Simply because if the sump is barely big enough for the first grow bed, it won't be big enough for two - and the second one might be a little bit bigger. I guess I could connect the two sumps with a bridge siphon, but that would mean tripping over the bridge, because it would be on the other side of the walkway in the greenhouse. Therefore I thought one pump could have hoses into two sumps, and suck it to the duckweed bed.

4: What is a veturi setup?

Ian Cameron said:

Well, lots of questions! While not an expert by any stretch of (my) imagination, there are some answers that come to mind.

1. How much water in your GB? Well, I figured about 40 -50% of total bed volume. That came very close for me using Hydroton.

2. Separate sump for additional GB. Why not plumb to the existing sump? Unless you plan on pumping back.

3. Pumps- submerged or not? I've had good results from both. But I prefer submerged. Less plumbing, and I believe it keeps pump running cooler.

4. Aeration? Absolutely. I have 2*12" air stones in each 75 gal GB, same in the 4*4 DWR, and 2 in the FT. Air is the cheapest way of promoting good growth in all aspects of my system. Also, on every water outlet I made a veturi setup to suck air in as water is passing by. Works like a charm. Fish are happy, plants are happy and I am happy:)

Hope this helps a little

[Ian Cameron]

Ummm.been thinking about this all day. Are you planning to draw from two separate sumps with one pump? If so, timing becomes an issue if you don't want to run your pump dry. That's why I was wondering if you were going to plumb the sumps together. You might be better served by another pump pushing to your duck weed tank. Just a note here, pumps push water far better than they pull it. I would hate to see you get everything together then find out it does not work. As for venturi's, the last 6 inches or so of any downward facing outlet pipe I drill a series of 1/16" holes on a 45 degree angle like this \II/ . The theory is that when water passes by a hole a low pressure area is created, thereby drawing outside air into the hole and the water. It works.                                                                                     

[Louise]

Thanks! I just realized I could connect the two sump tanks via a pipe under ground!

Venturi sounds like a great idea, I'll use it! Come to think of it, I even have a friend who designed a wonderful aerator called a vortex generator (based on Viktor Schaubergers 100 year old ideas, if anyone is curious about swirling water). I think I'll ask him if he has a little prototype lying around his workshop I could have. To buy one is far too expensive.

Thanks for thinking with me!

Ian Cameron said:

Ummm.been thinking about this all day. Are you planning to draw from two separate sumps with one pump? If so, timing becomes an issue if you don't want to run your pump dry. That's why I was wondering if you were going to plumb the sumps together. You might be better served by another pump pushing to your duck weed tank. Just a note here, pumps push water far better than they pull it. I would hate to see you get everything together then find out it does not work. As for venturi's, the last 6 inches or so of any downward facing outlet pipe I drill a series of 1/16" holes on a 45 degree angle like this \II/ . The theory is that when water passes by a hole a low pressure area is created, thereby drawing outside air into the hole and the water. It works.                                                                                     

[Jon Parr]

1. How much water in your GB? Well, I figured about 40 -50% of total bed volume. That came very close for me using Hydroton. AGREED, ABOUT 40%. 

2. Separate sump for additional GB. Why not plumb to the existing sump? Unless you plan on pumping back.AGREED, THE LOWEST SURFACE WATER LEVEL IS THE SUMP, REGARDLESS OF HOW MANY TANKS YOU HAVE HOLDING WATER, AND THE PUMP MUST GO THERE ONLY. IN GENERAL, TWO PUMPS SPELL DISASTER SOONER OR LATER. BRIDGE SIPHONS CAN BE ROUTED UP AND DOWN AND BACK AGAIN, SO LONG AS BOTH ENDS TERMINATE UNDER WATER (OR HAVE A PEE TRAP) AND ALL AIR IS EVACUATED. THEY ARE COOL, BUT THEY DON'T LAST FOREVER. VARIOUS FORMS OF BIOLOGY PRODUCE GASES, AND THESE GASES MAY (WILL) ACCUMULATE AND BREAK THE SIPHON. PLAN ON EVACUATING EACH SIPHON EVERY MONTH OR TWO. 

3. Pumps- submerged or not? I've had good results from both. But I prefer submerged. Less plumbing, and I believe it keeps pump running cooler. DITTO

4. Aeration? Absolutely. I have 2*12" air stones in each 75 gal GB, same in the 4*4 DWR, and 2 in the FT. Air is the cheapest way of promoting good growth in all aspects of my system. Also, on every water outlet I made a veturi setup to suck air in as water is passing by. Works like a charm. Fish are happy, plants are happy and I am happy:) AMEN. GOOD ADVICE. AIR IS ALSO THE CHEAPEST INSURANCE YOU CAN GET TO ENSURE FISH SAFETY WHEN PUMPS FAIL, OR WHEN POWER FAILS AND THE AIR PUMP IS FED OFF A SOLAR CIRCUIT OR BATTERY BACK-UP. 

[Jon Parr]

And since you asked for pointing out faults...

1- don't use IBC's for fish tanks. They suck. They are hard to keep clean, the plastic is not UV stable, they make catching fish difficult, and they are ugly. Of course those are my opinions, and there are probably a hundred folks from the IBC group that would argue. Use a round tank with a circular flow, and an SLO in the bottom center. It will stay sparkling clean forever. 

2- don't use a bell siphon. They suck. They are completely subject to inflow rates, and inflow rates are variable, period. Use timed flood and drain. Later when you add a grow bed, use an indexing valve off the single pump, or add a second pump in the sump and time it to pump on a different cycle. That would also aid in minimizing sump displacement volume, as only one bed would be filling at a time. I should modify my statement above about using two pumps. You can use as many pumps as you like, if they are all in the same sump, or if the failure of any one of them cannot cause water loss. 

3- don't use LECA. It's awesome, but the price sucks. Use large gravel, char, or lava rock. I prefer 1 1/2" size. Lots of room for roots, solids, and worms

4- a floating raft DWC trough makes a great sump, and serves as growing area. 

[Louise]

Thanks!

1: well, if I could find a round one as easily as an IBC...

2: I learned to dislike bell siphons too. But I don't particularly like the timed version either - how do you choose a good dimension for the small outlets? How about loop siphons, I haven't tried one of them, so I don't dislike it yet.

3: Personally I don't like lava rock, I have it in my indoor system, and it's a pain to dig in. I want something smooth. I have some LECA that I salvaged from work when something was rebuilt (roof garden), so the price for topping it up won't be hideous. I'm looking forward to digging with my fingers.

4: great idea! The way I planned the set up the light might be too low, but I'll keep it in mind for the next extention.

Jon Parr said:

And since you asked for pointing out faults...

1- don't use IBC's for fish tanks. They suck. They are hard to keep clean, the plastic is not UV stable, they make catching fish difficult, and they are ugly. Of course those are my opinions, and there are probably a hundred folks from the IBC group that would argue. Use a round tank with a circular flow, and an SLO in the bottom center. It will stay sparkling clean forever. 

2- don't use a bell siphon. They suck. They are completely subject to inflow rates, and inflow rates are variable, period. Use timed flood and drain. Later when you add a grow bed, use an indexing valve off the single pump, or add a second pump in the sump and time it to pump on a different cycle. That would also aid in minimizing sump displacement volume, as only one bed would be filling at a time. I should modify my statement above about using two pumps. You can use as many pumps as you like, if they are all in the same sump, or if the failure of any one of them cannot cause water loss. 

3- don't use LECA. It's awesome, but the price sucks. Use large gravel, char, or lava rock. I prefer 1 1/2" size. Lots of room for roots, solids, and worms

4- a floating raft DWC trough makes a great sump, and serves as growing area.