Hi Maureen. I had a system in Washington for a couple of years, and know a few others that have them that are relatively successful. Don Stark has more experience with a raft system, I stayed with the flood and drain beds, and had no problems. What are you using for a media in the pots in the raft? What types of plants are you growing? What are the nutrient levels? What is the air temp in your greenhouse?
Hi Rick thanks for the reply. Temp in the green house on a sunny day like we have had lately, can be 110 or 120. There is ventilation and I have grown in soil for years with no problem. At fist I used a kind of chunky seedling medium in the pots. I have switched to mostly perlite. Because the seedling medium was dirtying the water. I am using a raft system because I want to raise produce on a commercial scale and heard that cleaning medium is time consuming. As for plants I have had basil, pac choi, lettuces and some water cress. I keep replanting hoping that eventually things will work out.
Dr. James Rakowcy (not sure on the spelling) perfected the raft system, the UVI system, that you should study up on. If you have enough nutrients it sounds like you should be fine. I would try the clay balls, or maybe a pea gravel in the pots, or the coconut coir. Again, ask some of those using the raft systems for more help. Did you use salt to alleviate the stress on the fish? Salt can have an adverse affect on the plants. Are the fish eating well? What would you say the weight of fish to gallons of water in the system is?
I have read some of the Rakocy literature. The UVI system is enormous He has four rearing tanks with 2,000+ gallons of water in each. Its hard to scale down from that. I get the proportions though and have built my system around those proportions.
I used a product of live bacteria from Pentair to help the fish, and they are eating well, very well in fact.
I did learn that PH down that comes from pet stores contains sodium, that I read in Bernstein's book. That is when I first started seeing these brown edges leaves. So I took half the water out and replaced it.
I have just now tested the waters using test strips (its hard to get a precise reading from those) NO3 is at 20 and the No2 is at 0.5
For a long time I had 70 large Tilapia in a 100 gallon tank with 6cu ft river rock GB. Way out of proportion and I would loose plants or fish if I didn't change out half the water every week. Just too darn much nutrient in the water. After putting 60 fish on ice and adding a 5 gal bucket of oyster shell the GB perked up and became a jungle.
I have a question for y'all. how do you weigh your fish to determine if the proportions are right?
Hi Gerald, That is a great question. How does one weigh a fish thats alive and in the water? I feel another math problem coming on.
I have two koi that are about 5" long and three koi that are 3". and maybe five gold fish. I don't think the system is "overstocked" The entire system has 300 gallons of water. With the solids filter, degas chamber, sump and grow bed included. Maybe not enough nutrients?
It doesn't sound like you have much feeding the plants. How many fish do you have? What size are they? How much total water do you have in the system? I remember Dr. Rakowcy had as much as a pound of fish to a gallon of water. That of course is a really heavy fish load and you have to have a lot of plants to absorb that. I believe a healthy system is good at 1lb of fish to 5 gallons.
I have a UVI calculator, probably not the latest, that says 250# fish in 250 gallons fed at 1% total fish weight daily is OK with 250 feet media surface area and a 27 gallon biofilter, no solids filter required. Or 5 feet media surface area with 1330 gallon biofilter flow rate 277 gph and 145 sq feet of leafy greens either way. For what its worth.