Comment

Comment by Rob Nash on October 3, 2012 at 8:08pm

Steve, the fans help with air circulation, keep the plants strong, help keep the bugs down, move the cool air through the greenhouse, and make it more comfortable for me. ...fans are good.

i buy the cheap ones so i can have them everywhere.

Comment by Steve Chin-Yee on September 30, 2012 at 8:11pm

Whats the fans for?  Thanks

Comment by Rob Nash on September 13, 2011 at 8:16pm

the lights are left over from the winter. adds heat and speeds up growth. only on for 3 hours before sun up. the pics were taken in the spring.

Comment by Pices on September 13, 2011 at 8:13pm

Rob, do you need the grow lights to produce a crop, or are they just to speed things up?

Comment by Rob Nash on August 28, 2011 at 2:54pm

I have found the 3/8 to 1/2 inch to be ideal, the water stays very clean and the gravel does not clog. i have seen videos and pictures of folks using one inch, but have no experience. i would have to guess, it would work just fine, it may take a while to get "primed". just go with the smaller gravel in the beds, and only have one drain into the raft. its been my experience that the rafts dont mind the "quicker" flow of the siphon draining. FYI - i only drain one of the four beds into the raft, the other 3 drain back to the tank.

yes, i think the constant flow is too much for some of the plants that dont like a wet foot. Murray has shown that even plants that dont like a wet foot do well in an ebb and flow system. i have heard that in a side by side experiment, that the constant flow showed the greatest growth. i was unable to come to the same conclusion in my tests. 

Comment by David Waite on August 28, 2011 at 2:41pm

Rob love your design. Do you think your gravel being 3/8 inch is the right size or would you recommend 3/4. I am contemplating 1 inch rock as the prefilter then go to 3/8 rock then to the rafts. The concept of 1st bed being 1 inch with bell siphon drains to 2nd bed which is 3/8 rock that fills fast off the bell siphon of the first bed to drain slowly to the raft. Your thoughts would be appreciated. On another note do you think constant flood is just to wet day in and day out.

Comment by Rob Nash on August 28, 2011 at 2:23pm

Gina, these are a modified version of Tom Speraneo's ebb and flow design. The original design used ball-float switches on the pump as a sort of timer. As the water pumped out of the fish tank to the grow beds, the ball was adjusted to turn the pump off just as the beds were full, and then on again when the beds drained and the fish tank filled. As long as your water level stayed topped off, this worked well enough. But when the float switch dies so does your air supply, as the original design did not employ air stones.

I use interval timers to control the ebb and flow, and have added air stones to my tanks. Wow, what a difference O2 makes in fish growth rate!

I have a different system (not pictured) that uses bell siphons to control the timing, and of course it works great and i love it. I plan to retro fit bells to the production beds soon.

As for adding media to the first row of your system, you may have to rebuild it into smaller boxes which will not use all of your water to fill. three beds can be perfect, because one will drain in the time it takes the other two (really 1 and 1/2) to fill. Basically, time each one to offset the others. The sequencing multiport, I thought I saw on your site, would be ideal for the job.

And the real beauty of the Speraneo design is no dumping of the water from the separators. the gravel is the filter. Of course if you still use the separator and mineralization tanks the gravel will just stay very clean, and still thrive. you could even go back and forth between using the filters or not, according to how clogged your gravel is at the time. if the gravel starts to get clogged, you dont clean the media bed, just bring the filters back online,and you just let the gravel "wash out" some.

I am trying to avoid heating the tilapia tanks in the winter. I plan to add fish that i have overwintered from fry to 4-6 inchers in March. by the time November comes around, all the fish should be market size again and the gravel will be maxed out and in need of a break from the fish load. harvest all the fish and let the system wash itself out for the cold months while only growing winter crops. thus only having to heat the water a little bit, instead of the 74 degrees i had last year. when my normal $300 electric bill went to $900, i had to come up with a solution.

i will keep you posted on the results.

Comment by Gina Cavaliero on August 28, 2011 at 1:17pm

Rob is your gravel bed constant flow?

Comment by Rob Nash on August 26, 2011 at 6:41am

Hi Kobus, this is a Tom Speraneo "High Density" gravel bed. i run these at 1/2 lb pg.

they are 1000 gallon systems with 250 sft of grow beds. one of them is "pre-filtered" with a separator and mineralization tank, and it has 3/4 lb pg, and is doing great. the gravel stays clean, and pipes never clog.

I have one of them is connected the two 8x36 ft rafts you see in the other pictures. this hybrid set up is working great and will be my preferred method when i rebuild the farm at my new property.

Except for the one pre-filtered experiment, the other two are purely gravel beds. At the higher stocking rates, the beds do need to be cleaned between plantings, but are really no trouble. i have a “UVI style” raft, with separator and mineralization tanks, and it is more work and waste than I’m willing to except in my daily routine. I really like the ease of maintenance of the gravel beds. Tom Speraneo at S&S Aquafarm was right on with his design.

Comment by Kobus Jooste on August 24, 2011 at 11:35am

Hi Rob.  Love this system.  Is it a LD (Friendly type) setup running purely on gravel beds?