Raft Discussion
WARNING! There has been discussion among attendees of our courses about alternatives to the Styrofoam rafts we use (which were approved for organic certification by Oregon Tilth), and some of this discussion involved using plywood for rafts or portions of rafts in the troughs. Exterior plywood is glued with a urea-based formaldehyde-containing glue that is a known toxic material. Even if your organic certifying agency doesn’t catch this item, it will still leach off into the troughs and possibly kill or stunt your fish and vegetables. Even if it doesn’t, you will be feeding formaldehyde to someone down the food chain. IF you decide to use INTERIOR-grade plywood, because it’s NOT glued with the toxic glue, your interior plywood will degrade and FALL APART under exposure to moisture because it’s not designed to get wet! Use the Styrofoam rafts, they’re food-grade just like a coffee cup.
(Below) An awesome premanufactured raft by Randy Campbell, of Today’s Green Acres in Elora, Tennessee (email Randy about rafts by clicking here).
We use 2” Dow Blue Board Styrofoam “Square Edge” rafts for our aquaponics, and have had NO problems with them. This Blue Board comes in several OTHER configurations which do not work as well: one is called “Tongue and Groove” Blue Board, this is OK, but has a bump on one edge and a groove on the other which make them difficult to paint and also make the edges of the rafts more vulnerable to damage. Another type of Blue Board is called “ScoreBoard”, and this one is a pain because it has three scores down the long 8’ dimension of the sheet that are designed to help the sheet BREAK EASILY along these scores. It works: they DO break easily along these scores, when you are harvesting, planting, or just looking at them crossways. DON’T get “Score Board” unless you have no other choice, and then, cut your 2X4 rafts out crossways, with the cut lines going across the “Score” lines, not parallel to them! How do we know? 🙁
(Below) Making our own rafts out of 2″ Dow Blue Board; Tim is drilling through a 1/4-inch plywood template that makes getting the holes perfect EASY.
There’s another brand of raft foam; this is Owens Corning “Foamular”; it’s pink. To the best of our knowledge, after reading the Safe Use Instruction Sheet for this product, we feel this is just as good as Dow Blud Board, and should be certifiable by the organic certifying agencies. (Because this is not classified as a potentiall hazardous product, it does not have the standard Material Safety Data Sheet, or MSDS, but rather the Safe Use Instruction Sheet). Do not confuse this foam with pink polyisocyanurate foam, which we discuss in a bit; it’s not the same!
If you can’t find Dow Blue Board or Owens Corning Foamular, you can use that white styrofoam that looks like a bunch of little beads stuck together; it is food grade, just like a styrofoam coffee cup, but it is much weaker than the Blue Board. Cut it into 2 foot by 2 foot rafts, and it will last a lot longer than trying to put all the weight of mature vegetables on a 2 by 4 raft of this stuff.
WARNING! Do not be tempted to make your troughs a little narrower so the 48-inch wide raft will fit “snugly”. Some of our students came up with this idea on their own to prevent any algae from growing around the edges of the raft/trough space, and as a result, have created other problems for themselves. Here’s why:
First, the algae is not a problem. There is a very small amount of algae involved; it simply means you will always have a fringe of algae on the trough liner at the waterline, and on the raft itself. These are dynamic ecosystems, and this is OK; it’s how they operate! The mosquito fish and Gammarus will dine on the algae and add more nutrients to the system as a result.
In addition, you’re going to have a 1” PVC airline floating on one side of the raft in each trough, which is 1-1/4” diameter, leaving 1-3/4” of clearance for the raft. The trough itself, because of vagaries in the installation process (such as big rocks that you are trying to pound a 5/8” form stake THROUGH, which will make the form stake lean in or out instead of going straight up and down), will vary in width. It will be wider at points, and narrower at other points from the 51” inside dimension shown on the construction plans. Also, one of the main benefits of raft aquaponics is that the rafts float EASILY from one end of the trough to the other. A raft that fits snugly eliminates this benefit and will cause you hundreds of hours more work during the lifetime of that system.
WARNING! We have just been informed that the Benjamin Moore Semigloss Exterior Acrylic Latex Enamel, color “Brilliant White”, that we have been recommending for so long has now had mildewcide added to it, and the mildewcide is NOT listed on the paint can label! We do not have an “approved” new paint to recommend; this will have to be approved by your Organic Certification agency, and anything we could say about it would just be an opinion. But. What you need is a good quality latex semi-gloss exterior enamel with NO mildewcide in it. Try the paint out on your Micro System first, and get an approval letter from your organic certification agency for the paint you’ve selected.
WARNING: Do NOT use paint with mildewcide in it!!! This is a form of poison that is added to paint to keep mildew and mold from growing on your nicely painted surfaces. The poison will leach out into your water and kill your fish and plants! Make sure your paint does not have mildewcide in it!
WARNING! ALSO DO NOT use pink or white Polyisocyanurate foam rafts if you find them. These are often available the same places the Blue Board is, and are cheaper. Does “cyanurate” sound like “cyanide” to you? It is a related chemical compound and it is toxic; we have a report of one aquaponicist using it, and although his fish had been fine in the system for a month or so, approximately one-tenth of his fish died the week after he put the rafts in the system. We don’t know if the rafts were causal here, do you want to experiment and find out? They’re also NOT organically certifiable!
No, if I said that, paint me blue and parade me on Main Street. Find it if you can and send me the link; I’ll fix it.
We NEVER paint all the sides of the rafts, just the top, 2 coats. No, you don’t need to paint the sides, the bottoms, or inside the holes. If the algae that grows on the sides of the rafts and inside the holes grosses you out, you can spend a bunch of extra unnecessary time bleaching it off with hydrogen peroxide (organically approved) or chlorox (approved by Moms everywhere but not by the organic certification agencies).
Aloha, Tim…………
Benjamin Moore has changed all of their paint products and no longer mfr. semi-gloss latex enamel. Any suggestions for an alternative? I keep finding latex paints that are “mildew resistant” and suspect that they are not a good choice.
Benjamin Moore still manufactures the MoorGlo Semigloss Exterior acrylic latex enamel that we use; it simply is not being carried by some of their dealers any more. I just bought a 5-gallon of it last week at our local BM dealer. It’s some of the best paint I’ve ever used; covering in two coats what others take three or four coats to do.
UGL Latex DryLok? We have no idea what that is, have never used it, and cannot recommend for or against it. If you do use it, please report back on your experience after it’s been in your system for at least six months. Thanks!
BUT, “mildew-resistant” anything is always a BAD idea, because that means it has some kind of poison in it designed to inhibit mildew, ie “live things”. We’ve seen mildew-resistant swimming pool liners used in some people’s aquaponics system fish tanks (we DON’T RECOMMEND THESE!) and that is apparently related to some of the weird and not-nice things that happen in their systems.
Aloha, Tim……..
You can stakes at any WHITECAP SUPPLY. If you live on the mainland, they have the blue board too. Check their online catalogue.
I had a question about this foam board stuff. I can only seem to find the foam board with a plastic film on the board, seems like it might pull off, is it recommended to peel off the plastic film?
Also I’ve found 2″ thick at Lowes but it’s a 3.5 hour drive. I can get .75″ or 1″ locally and I’ve read that they can be glued together well with a polyurethane glue. I assume I’d definitely need to peel the film off the sides I’m gluing. Or is it not recommended to glue at all? I’m just trying to start a small system based on some of the Friendly plans I purchased, so don’t really want to drive 3.5 hours for just a sheet or two.
JD, I don’t know what the “recipe” for your “foam board” is. There are so many different types of “foam board” that we haven’t tried, and that we aren’t familiar with, that it would be irresponsible of me to comment without knowing much more about it.
“Dow Blue Board” is the trade name of the blue styrofoam sheets we use, and have gotten approved by three different organic certification agencies. About your “foam board? I can’t make an accurate comment; I’d just be guessing on whether or not it was safe or potentially toxic to use in aquaponics. As mentioned in this article, the white “bead” styrofoam is safe, with no plastic film on the faces. Can you find that stuff? It’s really common, even where the Blue Board is not.
As to gluing sheets together to make thicker sheets, that depends on the toxicity of the glue used. There’s some that are not toxic, and some that are; I suggest doing some research here. We don’t glue raft sheets together; we just get the right thickness to begin with because when you’re doing hundreds of rafts, it just makes sense.
What you can do, anytime you’re faced with a “materials safety question” such as this, is get the MSDS (Material Safety Data Sheet) from the manufacturer. Go online, enter the product name, manufacturer, and the letters “MSDS” in the Google search box. You should be able to find the MSDS, read it, and get an idea of whether or not your stuff is safe.
What you’re looking for in the MSDS is anything that says “Aquatic wildlife”, or “Safety For Aquatic Organisms”, something like that. Don’t worry about the stuff in the MSDS that says it’s poisonous when burned, EVERYTHING is!
Hope this has helped,
Aloha, Tim………..
Well the Dow Blue Board is just the stuff you recommended in your manuals. I found the exact same stuff. But like I said it has a plastic film on it. Being in zone 7 is just too warm for most stores to carry 2″ foam board.
I found the pink stuff also which your manual says is no good. I found the beaded styrofoam but that stuff falls apart just touching it.
Whether I drive 3.5 hours north to get the sheets of 2″ Dow Blue Board or I get the .75″ local stuff, it’s all considered “faced” which means it has a plastic film on both sides with the Dow logo printed on it. I don’t know if that needs to be peeled off.
JD, this is beyond our experience; we just get the right stuff, since using the wrong stuff can have so many unintended negative consequences. You can try peeling the film off and gluing it, just remember you’re going to need to find a non-toxic glue also.
I’d look around some more. Roofing supply houses and concrete supply houses (who sell those supplies to contractors) both carry the standard Dow foam with NO film facings, and you should be able to find some white bead styrofoam that isn’t so punky. We’ve used that stuff before in 2-foot by 2-foot rafts with good success; just handle it gently.
Aloha, Tim…………
Can’t locate them square 5/8 inch form stakes any where. Lowes and home depot only have round ones. I found these which are much the same as what I saw at home depot but round
http://www.ebay.com/itm/Concrete-Steel-Form-Stakes-3-4-x-24-by-Hartford-Tool/331812416059?_trksid=p2045573.c100033.m2042&_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20131017132637%26meid%3D11bd97c8afe846369b5e90c0f215fb4f%26pid%3D100033%26rk%3D1%26rkt%3D2%26sd%3D331812416059
Think they will work?
The round ones are fine. We’ve used 1/2″ and 5/8″ rebar before with “U” clips with screws to fasten it to the trough sides 2X4’s, but it was a LOT of work: after cutting the rebar, deburring the ends so they weren’t razor-sharp, and installing with the U clips and screws, we saved money by using the form stakes on our next system.
You can get them from concrete contractor’s supply houses too; and can sometimes buy used form stakes for half the price of new ones = they work just FINE!
Aloha, Tim…………
Hey Bob,
I used the round ones from Home Depot, sometimes you just have to work with whatcha got. GripRite seems to be the only company that makes the square ones. I called and they are only available in the midwest and you cant order them as a individual. Here is the product page, maybe your local building supply can order them? http://www.grip-rite.com/us/en/products/concrete-construction-products/steel-stakes
The ebay link you provided is exactly what mine look like, you can get them at HD and Lowes too:
http://www.homedepot.com/p/0-75-in-x-0-75-in-x-24-in-Round-Steel-Stake-with-Holes-50832/205026401
http://www.lowes.com/pd_9883-80032-831947_1z0y5pz__?productId=4008157&pl=1
Sorry I couldn’t be of more help,
-Jess
When painting rafts, do you only paint top side or all sides of raft? Thanks in advance
That is a great question Bob. The reason we paint the rafts is because the styrofoam is photo-degradable (meaning that the boards will disintegrate if left out in the sun unprotected). The paint acts as a barrier so the sun cannot degrade the foam, so that is why doing 2-3 coats of paint on the tops is important. You don’t have to paint the sides or bottom because they are not exposed to direct sunlight.
Hope that helps clarify things =)
-Jessica
Perfect! Happy holidays to you and your crew! Aloha, Tim………..