Component ratios and sizing are the problems I am wondering about right now. How do I know how much raft surface area I need in order to use up all the nutrients that I will be adding to the system. This is the system I am thinking about building:
Two 300 gallon fish tanks. One 300 gallon clarifier. One 55 gallon filter, and then the hydroponics system.
I have read that you need around 57 grams of fish feed/ m^2 of raft. Surely this depends upon the density you are planning on stocking your tanks at (I am planning for .25 lb/ gallon), and the volume of water in your system. I assumed that since the 57 g/ m^2 was based on a .5 lb/ gallon stocking density, I would need half the surface area, or 114 g/ m^2 of raft surface area.
Any help on sizing ratios would be helpful.
I have never heard of lava rock being refered to as cinder rock either. It should work well. It has a good surface area to volume ratio. It seemed expesive when I looked at it at a landscaping supply center, however I have not done much shopping for media yet.
I am impressed that the sea of green website has performance curves for their pumps. To use those graphs you need to know how much energy loss their is in between where you are taking the water from and where the water is going to, which, as Jonathan said, depends on how much water you want to pump and what you are pumping it through. The name of the graph you need to properly use those pump performance curves are called system performance curves. It is basically a plot of how much energy your design will lose based on how much water you are pumping. You plot both of those graphs on the same plot, and their intersection defines how much water your pump will move and how high that water will go.
Jonathan - I have no idea what the "most durable, longest lasting pump, ideally high volume, low energy usage and low price" pump is. lol! That is a lot of criteria, but they are the right ones.
As far as comparing raft grow beds to media filled grow beds, here is what Dr. James E. Rakocy has to say about them: Bad: 1) subject to clogging, 2) roots of plants are left in system after harvest. 3) Cleaning gravel is difficult. 4) Very heavy
Good: 1) No need for a seperate filter. 2) Easy to build with. 3) Can provide some nutrients to plants
Bad: 1) Plant roots are more susceptible to harmful organisms associated with aquaculture. ie: fish fry, snails. 2) Solids must be removed before raft system
Good: 1) Avoids clogging 2) Minimizes algae growth by shading water. 3) Rafts (just styrafoam) are easily moved and cleaned. 4) Ligth weight when compared to rocks.
That is a summary from Recirculating Aquaculture, by MB Timmons and HM Ebeling.
I have not decided which system I am going to go with, although after putting together that list I am inclined to go with a raft system.