Winter Growing

After some experimenting with grow bed media in the early winter, I planted my indoor crop of lettuce and rainbow chard in mid-January. After about four weeks the plants look quite healthy. All seeds germinated in the expanded clay bed, and I then transplanted a few into the gravel bed. I've given the lettuce in the gravel bed plenty of space, and I'm curious to see how differently the plants grow in the dense and spaced scenarios.
   

Expanded clay bed 2/3/2011

   

Expanded clay bed 2/9/2011



Gravel bed 2/9/11

The conditions in the water are not ideal right now: while there is plenty of nitrate (plant food), the pH is about 8 and the temperature is about 62-65 ^oF.

A pH of 7 or just below is ideal in aquapaonics. Plants absorb the most nutrients in slightly acidic conditions (pH < 7)  while fish prefer it slightly basic(pH > 7). So we compromise and try to make the water pH neutral (pH 7). The nitrificaiton process (turning fish waste into plant food) naturally lowers the pH, so the fact that mine is above 7 means other factors are at work. First, my gravel has lots of limestone in it, and the calcium it contains leaches into the water and raises the pH. Surprisingly, the clay pebbles also raise the pH, even though they are billed as pH neutral. I tested them by letting some clay pebbles sit in fresh tap water (pH 7) for a week, and they raised the pH up to 8 or 9. The plants are growing well now, but I'm going to experiment with adding some lemon juice to lower the pH over the next week.

As for the temperature, the nitrifying bacteria prefer water between 72-75 ^oF. At lower temperatures, their growth rate slows down significantly.  I could use water heaters, but they are very energy inefficient, so I'm trying my hand under cooler temps. The goldfish and lettuce, however, love the cold water. Currently, there is plenty of nitrate in the tanks, and I will monitor the tank to see if the bacteria are able to maintain sufficient levels as the plants near harvest stage.

Water Wheel Prototype

19th century water power is alive and kicking!....er, spinning! My water powered biowheel* prototype is complete. Pumped water powers this overshot-style wheel (I'm not quite ready for the Pelton wheel yet), which turns two attached drums. The drums are wrapped with multiple layers of fiberglass screen to provide surface area for nitrifying bacteria to colonize. As the wheel rotates, the bacteria will get a consistent does of moisture and oxygen, which will hopefully lead to vigourous growth and biological filtration (converting fish waste to plant food). You can see a video of the wheel in action below.

Now my wheel will go into test mode: I will fill the tank with fresh water and see if the wheel can provide enough biological filtration to effectively start up or cycle the tank.**

Friction was literally the biggest obstacle to getting the wheel moving. Specifically the wheel had to be able to overcome the resistance the tank water would put against the paddles. To combat this, I angled the paddles so they retain more water as they spin down and then release water as they start to spin upwards. Additionally, I just barely