Backyard Aquaponics
A place to discuss aquaponics

Got a chainsaw?

Hi Janet:
I emailed my ocean biologist friend about your sand column and he concurs that it should work. They use this technique in reef aquariums to process the nitrates to free nitrogen:

http://reefsources.itgo.com/guide/biological.html
http://www.reefcorner.com/Manual/nitrogen_cycle.htm

I guess you'll be monitoring things so that the columns don't starve your plants?

Great stuff, Dave!! I am monitoring the nitrates, and so far, there's no danger of the plants starving. My sand columns are in 4-inch PVC and are about 10 inches tall, so proportionately, they are very small. If I don't see much action, perhaps I will build another sand column. I have more sand and more PVC. Then again, maybe I could just dump a bunch of sand in the bed and let the whole bottom of one growbed be anaerobic sand. That seems to work in the marine aquariums just fine. Hmmm.....tougher to get out, though.

Janet, if your drains are set low in your growbeds you might need to use some soil barrier cloth to prevent the sand from running through your siphons and clogging the lines. (You can get it at Lowe's, HD or most other building centers. It will be back with the drainage line supplies.)

I was thinking about doing one bed just for things like lettuce/herbs in a sand growbed. I would use it as the final bed before returning the water to the fish tank. More or less to just "polish off" the water before restarting the cycling.

Kevin

Good point, Kevin. Interestingly, my drains are off the bottom about 1.5 inches. However, a soil barrier could be incorporated into the design. Hmmmm.....thinking thinking thinking.....

Maybe _not_ washing the gravel and having the drains an inch or two off the bottom is just the ticket to make this all work. (I know, that AP heresy, but most of what you wash out of the gravel is sand and mud. both of which would set up lots of sites for anaerobic bacteria.)

With you there Greenedo,the last of 6 GBS was experimentally added with shell grit and zeolite ,Hey isnt that the AP way? sorry J but im toolazy to go to my own site , have 4 wasshed beds 1as above and one unwashed! (probably not an AP er any more am i E ll?)

Well, I think it depends on what your gravel has in it. Mine was coated in a very fine clay. I think it would have packed solid. However, if you had no clay, and lots of finer sand in your gravel, that might be the ticket.

I was thinking about some gravel I got recently; it was crushed granite most of the run off from it being rain-washed was sand and some dust that turned the rain water milky. Not much clay. When I actually get around to doing it all, I might opt for the lazy-man's way - er, the anaerobic sand in the bottom....

blasphomy!

Lovin' it.

I decided I could get a few more liter's worth of filtration out of my growbeds if I added more gravel and raised the siphon loops. I stopped by the local soil/stone store and picked up another bag of gravel, but this time opted for a different color that I knew was taken from a sandy area, not clayey. (We have both around here.) It's nice stuff, a bit finer than the 3/8" river gravel I have, and it was mixed with a little sand. I dug it in -unwashed- to one bed that I nearly cleared out yesterday. (Spider mites, ugh). I took two cuttings from tomato plants in the garden, and tucked them in, and will decide what else to plant in there soon. The water is a bit cloudy, but I think it will clear by tomorrow.

Nitrates are now down to 200-300, and the Jungle portion of the growbeds is growing nicely. I also have some peashoots coming up quickly. Basil is starting to look tired.

I have kept pondering my challenges with ammonia/nitrite and pH...suddenly I've realized, it's probably all related. My pH is 6.0 (or lower ) and after re-reading Steve's Nitrogen Cycle post in the Helpful section, I've realized that most of my bacteria is on holiday! The pH is just too low for them to do much. How I have a 6.0 pH in a system with 28 pounds of crushed coral, I just don't know. But I do. I even added some fresh coral, but no effect after a week.

I remembered that James Rakocy (UVI) added something each day to bring his pH up, but couldn't remember what. After a bit of Googling, I found he alternated between calcium hydroxide and potassium hydroxide, depending on what was cheaper. He also recommended against sodium bicarbonate because it would negatively impact the plants. More Googles....calcium hydroxide is used in marine aquariums to provide calcium to the reef organisms, and to raise the pH. The name they use for it there is Kalkwasser-- I think that's "Chalk-Water" in German. So the brilliant thing is that this means I can get a small quantity through my favorite aquarium-supply store. (Just a kg, not a 50-pound sack.) I should have that in a few days, and will start adding very small amounts to try to slowly pull my pH up enough to help the bacteria get started again.

I may do a water change to pull the pH up a bit in the meantime. I know that will mess up the sand column - nitrate experiment, but I really don't like sitting at 6.0 (or lower)

Janet, how much are you feeding them these days? Mine looked hungry and the babies are big now so they get one tablespoon of the adults' feed and the adults get five tablespoons.

Mine always look hungry. They get 3-4 tablespoons in the morning, and again in the evening. (about 35g total per day) I'm hoping that if I raise the pH, my bacteria will do better, and I can feed more. For optimal growth, I really think I should be feeding them twice the amount that I am. At one point, I was up to 4 tablespoons 3 times per day (60g total per day), but the bacteria just won't handle that right now.

Janet, is there anything you may have done recently to drop the ph so low?