Wednesday, July 23, 2008


New DWC Growbed
Here is my newest picture, showing off that shiny new dwc growbed.

In Other news, I purchased an FishMate p21 automatic pond feeder from PetsMart. I liked the digital ones better, but when I got to the petstore I realized they would hold maybe 3 days worth of food, max. The P21 should handle the feedings for the whole time we are gone. It uses what looks like a clock mechanism to rotate a drum that spins once every 24 hours, and dispenses an amount of food controlled by adjustable baffles. It is setup over a bowl in the garage right now, testing to make sure it works, and that I adjusted the baffles for the appropriate amount of food. Tonight I'm going to change 1/2 of the ammo-carb media in the filter, and that should control the ammonia and nitrites until we get back. Then it is back to the process of inside-outside water changes.

Corn does better in gravel than DWC.
Lettuce does better in DWC than gravel.
For green growth, Tomatoes seem to do better in DWC, but the gravel plants may just be crowded.
Oxygenation seems to be the limiting factor in the DWC beds.

Lessons Learned:
When planting seeds, label them or draw a map. I have a HUGE viney plant, the trunk is about 2 inches in diameter, right behind the corn, and no idea what it is.
Oregano seedlings need to be more developed before transplanting. Every one of the Oregano seedlings baked off or was eaten by friendly caterpillars.
Caterpillars are evil.

Friday, July 18, 2008

One weeks growth


The picture on the previous post was taken Monday. This Picture was taken today (Friday) . This much growth in less than a week blows my mind.



Thursday, July 17, 2008

Transsexual Tilapia

There was an interesting blog on the Washington Post about sex-reversed "Transsexual Tilapia."

I hadn't considered marketing fish to Whole Foods market, but it makes a lot of sense considering our overlapping target markets. I will have to have a conversation with someone over there. Related to this, I found an organic feed supplier. Combine the ideas and I should be able to provide chemical free organic clearwater male hybrid Tilapia. That sounds marketable to me.

Onto another note, I transferred 5 fish from the inside system to the outside system over the weekend. That night I had a hose slip off and pumped about half of the water out of the system. We caught it in time and I refilled the system from the water change barrel. The transfer stress followed by the sudden 50% water change stressed the fish, and 2 of them didn't make it. The others seem to be recovering okay, and the plants are growing well with the extra nutrients.


Sunday, July 6, 2008


The Southern Regional Aquaculture Center has a good PDF on the UVI Aquaponics system.
SRAC Paper on the UVI Aquaponics System

I have some more results from the last batch of seedlings. Planted in rockwool, Tomatoes 100%, Corn 50%, and Oregano 10,000%, germinated and are growing well. The spinach, daisies, and sunflowers did not germinate. I transferred the seedlings to the dwc raft and terminated the remaining cubes. The seedling tray is out on the deck baking in the sun.

Lessons learned:
Algae grows on rockwool cubes.
Flies are really attracted to grow-lights. Then they drown in the plant water and it is icky.
Some plants, especially spinach, need different techniques to germinate.

That last point matches what I learned from the Cornell manuals on hydroponic production.

The links to the manuals are broken on the Cornell site, but I was able to find them with some google hacking.

Cornell Manual for Pak Choi Production
Cornell Manual for Spinach Production
Cornell Manual for Lettuce Production

In my other readings this week I learned a few more things. Commercial Hydroponics typically uses reverse-osmosis filtered water to eliminate buffering from the dissolved minerals.

I've been considering Ferrocement for the fish tanks. I think that the labor on that is going to be too much for me though, and purchasing a commercial tank or above ground pool remains a better option.

Here are some ferrocement resources
Building a FerroCement Water tank
a Youtube ferrocement tank video, much less "overbuilt" than the ones in the manuals
(removed dead link)

And finally, Catholic Relief Services Ferrocement Manual

It looks like the fundamental equation is managing the fish feed to hit the right nutrient levels for the plants. More fundamentally, balancing fish food and plant production. Everything else, Fish counts, DO, growbeds, rafts, etc, is just supporting the fundamental balance of fish food to plant production.

I replaced the grossly underpowered air pump in the dwc bed with a $20 Wal-mart air pump and a bubble wand. There was a significant amount of solids on the bottom of the DWC bed and the fish tank. I removed the inlet filter from the pump to try and help with this. Hopefully these two changes together will get the solids in the gravel bed where they belong.

The squash are showing tip burn. I'm going to point the fan at the beds tomorrow and see if that helps. The Cornell manual says that the tipburn is because of insufficient transpiration where the plants have nutrients and oxygen for a light level, but not CO2. Another balance. Light feeds respiration which requires nutrients, oxygen, co2, and water. With no greenhouse or shadecloth to manage the light levels, it is worth playing with the other variables to see what happens.

This is fun.

Friday, July 4, 2008

Nibble Nibble

The tank was a little low this morning, so I pumped in some water from the water change barrel. The white fish ate, but I didn't see the little fish. I ran my hand along the bottom of the tank and found a dead fish and a thumbtack. I saw another rather rough looking fish in the tank, not dead. I think the tank has the white fish (healthy or nearly so) the little fish (getting better) and the rough looking fish. The white fish took some pellets this morning and this afternoon, so that is good. I could be mistaken, but I think the plants look a little better too.

Time for more patience.

Tomorrow I'll do a water quality panel on both tanks and see how things (chemically) are doing.

I hate patience.


Wednesday, July 2, 2008

Here fishy fishy

It's been a busy week since my last post, but I have some good news. One of the fish wasn't really dead, only mostly dead. I discovered this while examining him looking for some indication of the problem. He flapped at me quite sternly, causing me to jump and eek. Suitably embarrased and encouraged by my son's laughter I took some pictures of the ailing fish.

Two dozen fishkeeping websites later, I believe my fish had a bacterial infection causing fin rot and bloating. This was most likely caused by trasport shock in moving to the aquaponics environment. This was further exacerbated by my attempts to solve the wrong problem.

I added 450 grams of Morton Kosher Salt to the system to bring the salinity up to ~2ppt. The fish have significantly improved, though I euthanized the mostly dead fish. Last night and this morning I saw three fish alive and swimming in the system, and they ate a few pellets. This is a really really good thing, since I haven't seen any of the outside fish eat _at all_ since moving them out.

On the business side of things I am expanding my search beyond lettuce dwc production. The idea of being tied so strongly to a single commodity product is unpleasant. I think some variety would reduce the total risk.

Hoping for continued improvement,