In answer to your question Sylvia, "why Styrofoam", meaning why bring up the subject? In my case it was a sheer reaction to seeing Styrofoam raft materials used in so many existing setups, and being promoted in training packages and so forth, including use as plant containers and trays of various types. Coming from an age of 'converting' the fast food movement away from Styrofoam, being one who can taste the Styrofoam in a cup of coffee, or on a plate of food, someone who is aware that styrene has spread into the bodies of all living things on earth, and that our oceans and shores are being plugged with plastics that don't go away, the particles only getting smaller and more insidious; I was amazed at the acceptance of it's use and incorporation in systems that are touted as organic and wholesome - only that -- a simple reaction!
My recent, (and short) learning curve, with aquaponics, is due to the fact that I will have about six months worth of time to work on a system in a third world situation, starting Oct/Nov of this year, and a raft system is a definite possibility, if not this year, possibly next, and have the better part of a half acre of land to work with, as well as local labor. Being in Central America, there is a supply of clean graded volcanic rock, and also clean graded granite rock available for use in trenches, ditches, trays, or other form of grow beds - leaving the question of cleaning the materials some time further down the road - again the question of raft systems arises - and of course the use of Styrofoam, - because it is available, - but it is not meant to be in the sun - (or near food?)
The "thin flexible mats" seen in many of the excellent videos, designed to hold plants, shade the water against algae, and allow for the raising of (some) shrimp in raft systems; are likely made of unicellular foam (plastic), similar to what is used in construction sites to - separate wood from concrete (1/8" thick); - also used in a thicker form (3/8" to 1/2") to cover and insulate swimming pools. Some of these products are actually designed to be in the sun full time, therefor would not break done as rapidly as styrofoam, even though the Styrofoam could be painted, as suggested in some of the 'package instructions' promoted in some the aquaponics media. These (higher quality) mats would of course need to be ordered from specialty suppliers, are not as readily available at the corner lumber yard, meaning costs would need to be figured out, including shipping.
Seeing as how the property in question for a system has a drop in elevation of about 30", dividing it at the 1/3 mark (of about a 1/4 acre total space), there is an option of a bed system at the lower level, and a raft system (eventually) at the higher level - as a possibility. Because it is in Central America, - money is an object, - wood rots rapidly, and is enjoyed by termites, - as well as (my) long history working with concrete, most of the parts and pieces would (eventually) be made with (reinforced - ferro) concrete for tanks, later for beds as well, using plastic (yuck!) lined ditches to start with - "yuck" - because any reasoning to do with Styrofoam also applies to plastic sheets, including sun exposure - as well as being readily available at the corner store, therefor easy to get.
The learning curve with aquaponics began with two assistants wishing to continue their (temporary) employment, and a vague idea of 'raising fish' - therefor a twelve (or so) foot diameter hole in the ground, four feet deep developed at about the breaking point in the elevation of the land, making it possible to consider draining the (upper) beds directly back into this 'tank' - which could end up (now) being the last one built! The learning curve so far has included reading virtually everything on this site, and every other thing and site available on the net even remotely connected to aquaponics - meaning I'm just beginning to learn; - a long history of gardening, and raising ornamental tropical fish also fits in there somewhere
At the moment am considering the purchase of two reference books, one "Recirculating Aquaculture", the other "Tilpapia", but in trying to find the sources, realize there is a huge body of free info not yet read. -- Normally not very verbose, I am simply responding to the question of "why styrofoam" - any further input is much appreciated
These are the two books referred to as being possible purchases, for further study, any input from someone familiar with either of these two books would be appreciated, as they do cost!
"Recirculating Aquaculture" "Tilapia"
When he asked "how will you clean it?" Was he meaning the initial washing of the gravel? Or did he mean cleaning as in maintenance?
In a media bed system, provided you put in twice as much media bed volume as you have fish tank volume, and don't over stock the fish tank. The media beds should never need "cleaning"
Clairifiers and filters not required in a media bed system so long as you have enough media beds to handle the solids. The flood and drain action provides the aeration needed to take care of the mineralization and composting worms help with that. So long as your gravel is large enough, clogging is not an issue.
(Now if you go cascading the beds so that the top bed gets all the flow from the fish tank and then feeds the next bed, the top bed will get too much solids and may need cleaning out, I recommend that each bed get it's flow from the fish tank so they can all enjoy the expanded nutrients from the mineralization of the solids.)
While if you go with a raft system, some one needs to clean the clairifier daily if it is a heavily stocked system or if you want to avoid all that, you need to go with an extremely low stocking level of something like 9 fish per 4 x 8 raft and those beds will need to be cleaned out occasionally.
Good Luck on the research.