Sand Experiment Update

Started to notice some yellowing in the leaves of the basil and tomatoes, so I'm guessing that I've run out of useful nutrients. I guess I made it about 10 days.

I'm going to supplement the nutrients as I would a normal hydroponic setup to see if a twice per day flood is adequate for the plants.

I'll be moving the first week of August, so my experiment doesn't have too much longer to run. It's a race against time to see if I can get some harvestable cilantro before I have to dump all of my sand/gravel for the move.

Sand Update - Long Overdue

Well, it's been a long time since I updated the blog about the sand system. I blame travelling too much (at first), and then the heat of summer (lame excuse). Anyway, I'm sad to report that the sand system is proving to be too much trouble than its worth. After adding in some more river pebbles to the top to try and ease the surface ponding, it was only a couple of days before it started ponding again. I then tried to dig the inflow deeper into the sand, putting it flush against the bottom layer of pebbles. It wasn't two days before one of the beds began to develop a quicksand-like mush above the inflow, and surface ponding began again in earnest. I was initially optimistic and pleasantly surprised, as I was able to increase the inflow to full throttle after I buried the inflow. But, like I said, it didn't last.

Despite the surface ponding, the system works. I just don't like the water on the surface. It just feels wrong. I was able to do a taste test between a sand-grown tomato and a hydroton-grown tomato, and I have to say that the sand-grown tomato was noticeably tastier. My wife confirmed my impression, as well, and hers was a blind test.

In addition, I'm happy to report that our house is finally under contract. If all goes well with our home inspection and appraisal, we'll be closing on 8/15. I'll be sad to leave this place and my aquapondics and everything else, but I won't miss the commute.

In preparation for leaving, I thought I'd put the sand system through one more test. I took out all the fish. There's still some solid fish waste and other junk at the bottom. I've switch the pump to come on only once per day, at noon, for 45 minutes. [EDIT: I'm going with twice per day, once at 10 AM and once at 4 PM, each for 45 minutes.  It was getting too dry in there] My thinking is that if the damn things are going to mimic a surface flood, then I might as well try to treat my grow beds as if they were a floodplain. So, this little experiment will see a) how long do fish waste nutrients last when only cycled through grow beds once a day, i.e. how long will that old fish water provide for the plants remaining in the grow beds, and b) how will the plants do with just two waterings per day. My sand beds still have one tomato each, and I also seeded them with cilantro. There are a couple of other random veggies in there still, like cucumbers and sweet peppers. So, there's an array of different nutrient requirements in each bed.

This little experiment may prove extremely important, as it may imply that you can power many, many more sand beds off of one fish tank, when you only flood the sand bed twice per day. Imagine having a single 100 gallon tank, and then maybe 4-8 50 gallon grow beds of sand/pebbles, each getting flooded only twice per day? Sounds pretty awesome, to me, and it would probably mean that you could get the density of fish in the water up to commercial-like levels.

Added some pea gravel to the Sand System

My original load of sand over time and under pressure of water has compacted, and some of the roots were starting to show, especially when I was digging my channels around the sides. I decided to add some pea gravel to the sides to see if it might help to keep some of the algae from forming. So far, it seems to be working. It's been almost a week, and there's no sign of algae on the new pea gravel. The water seems to be flowing just under the pea gravel's surface. Plan is working!

Added the pea gravel only to the sides where the water flows around. You can see the algal mat covering the sand in the middle. Much of that sand "flooded" before when the mat built up enough around the sides when it was all just sand. 

Things are looking good, despite the lack of sun.

Sand System Update

Green beans starting to take over. Wish I had paid more attention to the seed packet and selected a bush variety!

Cherry tomatoes starting to ripen already.

Same photo, other side. You can see a cherokee purple getting larger.

I'm still happy with the sand system. I'm not sure it really has any advantages over other media, since it does require a fairly regular - every 2 days - brush off of the algal buildup. It's also unfortunate that the spot I chose to do this experiment has gotten pretty shady. It will be hard to judge/compare growth, as my aquapondics grow beds get much more sunshine.

The sand is definitely compacting. I'm planning on adding another bag of sand to top off each of the grow beds. I'm considering getting pea gravel instead of sand to try and minimize some of the algal mat effect - hoping that the increased distance between the gravel will still allow water to percolate through it. The sand gets so covered in algae that the water starts to pond.

All in all, though, things are going quite well!

BTW - these photos are over a week old. I tried for at least a week - maybe longer - to log in to submit this post on Blogger, but it wouldn't let me log in. Something was very wrong system-wide apparently, and it took Google a surprisingly long time to figure it out and fix it (in my opinion).

Very Quick Update

Had a busy weekend, so I didn't get a chance to get any photos, but I wanted to put out a couple of updates. First, I picked up 40 tilapia on Thursday. I initially put 15 into my sand system. However, Thursday night and Friday night dipped down in the 40's, and I was worried about the cool temperatures and the effects on the fish. So, I moved as many as I could into the pond. I got all but 2 out. The other two remaining were small and too damned fast to catch! I also lost a large one, who jumped out of the tank during the first night. Sad.

The tilapia in the pond seem to be OK. I've seen several feeding, though not all. I transferred 3 large goldfish into the sand system, so that is now holding 3 large goldfish and 2 small tilapia.

I've discovered that I don't need to poke holes in the sand. All I have to do is scrape away the algal mat on the top. I scrape it away in large chunks and then move those chunks to the surface of the sand under the plants (where the water doesn't get to). It should provide a bit of a mulch layer.

In my pond system. I've discovered that some other bugs are the major culprit in eating my strawberries. I don't know what they are, and I'll try to post a picture soon, so that someone who does know can identify them. They're extremely common around here. I've seen them in my compost piles, too.

I put in 3 uniseals in my three grow beds where the open hole overflow drains were, and I put in 2" pipe with elbows. When I flip them up, it serves to prevent water from overflowing out, so that I can flood my plants and get rid of the pests. It seems to be helping quite a bit, and I'm wondering if there are benefits to periodic flooding of the plants that I hadn't thought of before.

It also brings to mind the likelihood of growing rice in my system. I'm definitely going to look into it, as I think it would be quite easy to start off with less hydroton and keep adjusting the flood height and adding hydroton. I think that's how it works! Like I said, I need to read up on it.

Progress Report on Sand System

Thought I'd post a little update on the sand system before I add in 15 tilapia to the mix. So, the growth that you see is the product of 2 good-sized goldfish - that's it. I've seen good growth in the tomatoes, and all of my seeds have germinated. I will say, though, that it seems like the seeds may have taken longer to germinate than they did in my hydroton system. Could be that the weather is the major factor in that, though, as it's been exceptionally cool and rainy this spring.

Veggies include tomatoes, green beans, edamame, cucumber, yellow squash, sweet pepper, and some basil starting to come up.

Top shot shows the grow bed when the water starts collecting. Bottom shows what it looks like after I poke a few holes in the sand with 1/2" PVC pipe. Many claim that I won't be able to keep this up for long - that the sand will compact and clog and eventually stop draining well. Maybe... but for now, things are fine with the occasional hole poking.

All in all, I'm happy so far with the sand system. Having to poke some holes into the sand to help with drainage isn't that big of a deal work-wise, but the fact that it requires any extra effort puts it at a disadvantage to my hydroton system. It will be interesting to see how the drainage fairs  over time. I think most people think it will get clogged and basically crap out. I sure hope that doesn't happen!

Early Season Update

First, an update on my sand-based system. I noticed today that the water was collecting on the surface of the sand more than usual. Turns out that an algal mat is forming, and as a result, the water was having a hard time permeating into the sand. This is to be expected, and it's not a big deal. In fact, I think the algae will play an important role in the nutrient cycle for the plants I'm trying to grow. Problem was easily remedied by poking a few holes in the sand using a piece of 1/2" PVC pipe.  I imagine I'll have to do that regularly. Luckily, I planned ahead for something like this, and created channels in the sand around the outside of the grow beds for the water to move through. Since I don't plan on planting anything in these channels, I'm not interfering at all with any of my plants by poking holes into the sand.

My pond-based system is cranking along nicely. I'm in full swing in terms of spring veggies. See photos below. I'm particularly excited about the strawberries. They look fantastic, and there look to be a record number of berries on the way. I thought of a new term today for my system: "aquapondics". You heard it here first!

Cilantro in rear (left), arugula in rear (right), spinach in middle, and broccolini on left/right front

Strawberry grow bed. This grow bed is devoted entirely to strawberries, and they survive year-round (even when the entire grow bed froze solid with ice this past year)

Two tomato seedlings just planted on left, spinach in the middle, broccoli on right (with some leftover cilantro growing up in the spinach)

Pond with grow beds in the background

Sand System Refined

The spider valve is too flaky. Sometimes it would switch over to the next channel, sometimes it wouldn't. When you're talking about the difference between routing to a grow bed or just returning back to the fish tank, you're talking about the difference between life and death for both fish and plants. I couldn't depend on it, so I took it out. I will say, though, that the manual says that the spider valve should be the highest point in the connection, i.e. that all the water coming out should flow back down. In order to use the least amount of pipe, I didn't follow that suggestion. So, it could be that the spider valve works great, but because I didn't set it up properly, it didn't work. I can't rule it out, but with this experience, I'm not likely to try it again. Besides, it takes a pretty good flow just to get the damn thing to seal itself and work right. It's not worth the extra $$ expense on electricity, since you get an aerator that pulls only 5W.

Anyway, instead of the spider valve, I used my smaller pump (630 GPH - probably still oversized) and connected it straight to the two growbeds. I bought a Coralife Luft Aquarium air pump and an airstone. I then used a housing that I had for my old digital timer/relay from a couple of years ago to make the air pump weather proof. I had to drill a couple of holes - one to allow air to come in from the bottom into the housing, and one for the power cord to go out of. I used a little piece of old liner and some screen material to ensure that no critters could get in, and I used some pieces of foam to fill in the gaps around the airpump inside the housing to reduce vibration.

Housing for Coralife Luft pump

In full operation, you can see the return line draining in and the bubbles on the bottom of the photo from the air stone.

Both growbeds during a flooding stage. I carved little channels around the outside of the grow beds for the water to move through. Just like at the beach!

The whole system - fish tank on the ground, grow beds up on the deck, with drain pan underneath.

The drain pan is way oversized. I had that 3X3 Botanicare tray, and it seemed a waste just sitting there. It fit nicely width-wise under the 2 grow beds, but it doesn't need to be as large to do the job that it's doing. In fact, it's size means that more water is stored temporarily in the drain pan instead of providing the fish with more gallons to swim in.

All I need to do is to build a box wide enough and deep enough to serve the same function, but I don't want to spend any more money on it right now!

We're supposed to see temps near freezing tonight and early next week. As soon as that passes, I'll start planting.

Sand System Completed and Cycling

Well, the weather's warmed up enough to feel comfortable turning on the sand system to cycle it. If it does decide to get cold again, I'll shut it down. There are no plants or fish in it right now, so turning it off won't hurt anything.

A couple of notes about the spider valve. First, it requires a good deal of pump pressure to work. I had to use a more powerful pump to get it to function properly, or at least to get it to switch properly. Second, while it does divert the flow, I'm finding that there is flow coming out of at least parallel channels if not all channels. This may be due to the fact that the spider valve is located below my grow beds, so there's a little bit of head to climb before the water comes out, but I'm not sure.

In my system, where I want the flow to move slowly through the sand, it's probably not an ideal way of doing things. In hindsight, it probably would be best to have a slow pump going to both grow beds and an aerator running constantly versus using a spider valve to switch between the growbeds and using the two un-used feeds (there are 4 channels on the spider valve, and I have 2 grow beds) to cycle the water around in the tank for aeration.

We'll see. I'm also curious to see if the sand system is more efficient at removing the nutrients. It had better be, because I'm probably only running the entire volume of the fish tank through twice a day - again, due to the slow inflow.

100 gallon Sand System

So, many of you may not be aware, but the very first aquaponic systems (though they weren't called that) were actually sand-based. Dr. Mark McMurtry did his PhD work on integrating aquaculture and hydroponic growing methods, and after years of research and experimentation, he settled on using sand. The amount of surface area for the bacteria to attach to is orders of magnitude greater than any other growing medium.

So, inspired by that, I've been putting together a small, sand-based system.

I started with the fish tank I made last year (still need to reinstall the liner, which hopefully doesn't have any holes in it (see my notes on this later!)) positioned on the ground under the shade of a magnolia tree. I'll use one of those 4 way spider valves and run one to each grow bed, and two right back into the fish tank at the bottom, to try and flush up any solids. I also plan on having a small aerator in the tank running continuously to keep the fish happy.

I set up a couple of similar, though approximately 1/2 sized boxes up on the wooden deck above as grow beds. I set them up on cinder blocks, so that I could put the 3'X3' Botanicare tray that I bought last year and haven't really had any use for. The tray's purpose is to catch the water coming out of grow beds and any potential sand that might slip through the crack. My thinking was that having a separate water catcher might help to keep the sand out of the fish tank. The grow beds are lined with liners. They are actually two different kinds. One is an EPDM liner that was left over from my pond installation, but is a few years old. The other was one that I bought from Lowe's, and is a kind of mesh-looking thing - something like a glorified tarp that is supposedly fish safe. The orange straps are part of cinch down strap for the top to keep the liner in place as well as help to keep the box's shape and integrity. I ran out of wood, and figured while I was putting this together, the straps would work just fine. The drain pipe right now just goes into the yard while I'm washing the sand. By the way, I put in 4 4X4 with footers under the beams supporting the grow beds to try and keep the deck from falling under the weight.

Here's a look at the grow bed. The pipe at top delivers the water in what I hope will be a somewhat reduced flow rate. I expect that channels will form, and in fact, Dr. McMurtry mentioned that this would happen. The grow beds are tilted slightly to aid in the water flowing to the drain.

A closeup of the inflow system. It's got 1" pipe inside a 3" pipe, both with end caps. The 1" pipe has small holes drilled into the top of the pipe, while the 3" pipe has some slots cut into it on the bottom.

Here you can see the slots.

A view from under the grow beds. I cut a long slit the width of the grow bed to let the water drain out and stuffed the liner through the slit. It's hard to see in the photo above, but maybe if you look at the larger version. Anyway, the extra liner serves as a kind of a water bladder, and then I just cut a hole in it to let the water out. This was the best I could come up with, as I was worried about water choosing it's own path to go if I just cut a slit in the liner without stuffing it through the crack.

Above the crack, I put some fiberglass window screen material to try and keep the sand in. Dr. McMurtry used something similar, and he said that even cloth or clothing would work. That said, in my initial test, I did see some sand wash out. I expect some sand to come out, and I'm hoping it's a function of how fast the water is flowing in. The nice thing about the water catchment is that I can just scoop up the sand and put it back into the grow bed. But, if it starts coming out profusely, I'll be in trouble!

This is what I put into the grow bed. First, two bags of pea gravel, then 3 bags of multi-purpose sand, and then 3 bags of fine grain play sand. Hopefully there aren't any weirdo toxins or anything like that in the sand.

So, here's the rub. After first testing both grow beds for leakage by merely filling it about 1/4 full of water (before I cut open the slit) and finding none, I filled one grow bed with all the gravel and sand and tested again. Uh oh! This time, a leak developed that was pushing water out the bottom of the grow bed. My theory is that there is a small leak in the liner somewhere up along the lowest wall, and that I didn't see it initially, because I didn't fill it with enough water. This is the EPDM liner that is several years old. I kept it folded carefully and away from any sharp objects and the like, so I'm really surprised that it leaks. I sure hope my pond doesn't have a leak somewhere, too!

In addition, in the other grow bed, I found a leak in the bladder on the opposite side from where I was planning to cut the slit to drain the water. This is especially troubling, since I just bought the liner 2 days ago. So, right out of the bag, the liner has a hole in it. This is the mesh-like liner from Lowe's. As a result, I would strongly recommend AGAINST anyone ever buying this product. 

So, I'm at a crossroads. Do I continue, knowing full well that I have a leak in one grow bed that's already done with all the sand AND a leak in the other grow bed with a crappy liner? The only way this isn't a show stopper is because of my drain pan. Right now, everything drips into it, even the leaks. But it means that the boxes won't last long (hopefully at least a season).

Or, do I quit now and cut my losses? Perhaps looking into pre-made plastic tubs that would suit my purpose, cost more, but be less likely to leak? Or just do what everyone else does and use hydroton?!

What would you do?

UPDATE 2/7/11: Predictably, I decided to press on! I guess I'm stubborn (stupid) like that. Anyway, I fixed the small leak in the mesh liner box with some fish-safe silicone. The other bed I'm hoping won't leak once I slow the flow down to a reasonable level. I was testing with a garden hose on full blast, and the flow won't be nearly that high.

I'm almost done with the set-up. I need a few more feet of PVC before it's all said and done, and I hope to get to the store this afternoon to finish it up this evening.