On the next res change, just run one or better yet two municipal water res-fulls through at the highest flowrate that is comfoprtable (return water will get dirty, dump and repeat till runs clear) It won't hurt to pull out each plant and tenderly wash first in between, unless the roots are too stuck in there. That water will have a reasonble EC all by itself and be loaded with Algacide!

Observe where the algae grew. If it is only on the roots you might look for some cover for the net pots. If it is along the channels everywhere, it is because the material is just too transparent and you just need to figure out how to paint, wrap or laminate with something it out after finally tearing down.

I am intending to wrap the next channels to go into the system in foil. I think grizz man recommended that. Then I can pull the nursery Chanel's, clean and do the same with them. It is the return pipe and resivour that I want to try not to disturb.

I was thinking when I do the next fluid change and add the next 4 channels with wider spacing I may just flush all the old troughs and and drain, clean the resivour and bury it, well there goes a half day lol.

I have some alge on the tops of the rockwool but I am not as concerned with that as I am with what's on the roots.

Well, just make sure the top of the rockwool isn't the algae nursury. Grizz is definitely the man and he has a good way to stick foil which I'll also be testing out.

For the moment, I plan on getting two spray cans of Krylon Fusion brand spray paint for my channels if I run into this problem. One exterior black first coat and one white surface coat over it. Maybe the white will be enough, someone probably knows this here.

I'm estimating in direct SE sunlight it will last at least a year before needing a new white coat. Haven't tried it yet since my system isn't running yet, and I was hoping/planning my plastic was thick enough but have that as a back up idea since without actually trying either it sounds a little neater and faster. How well it performs - don't know.

Rio,
you needn't clean off the roots if you get the channels covered. the algae can't live in the dark. and not having the channels covered is the source of the problem. That is exactly why I started covering mine. The reduction in radiant heat was just an extra bonus.
Pupilla
Spraying your container black then white will definitely work, but the cost will be a lot less if you attach aluminum foil to it. the glue will last for about a year if you use spray on craft glue. you could buy a can of car liner spray on glue (it is a lot more heat resistant) and the aluminum would probably stay on forever. Well, you'd get tears in it before the glue released.
If you decide to go the aluminum route just be sure to glue it on the bottom of the troughs so you needn't worry about contaminating where the roots grow.

I am going to add a cover on the drain end and when the tank is buried the only place It will see light is in the 2 foot clear section of feed tube. I want to leave that in so I can see the flow for now. Once I trust things a bit more I will run black plastic all the way to the resivour.

My resivour has alot of what looks like dead alge in it now, we are doing a change this weekend. I will clean everything up then.

Rio,

Sounds like you'll have it under control. I'm sure Grizz speaks with more experience about not necessarily rinsing out the roots. But I think it depends on what you are growing too which wasn't clear to me. Once the light problem is licked, dead algae could possibly cling and get slimy if the oxygenation design of the system allows that when the roots get big for longer hauls. So if it is is a short time to harvest sure, but if your are keeping something for months you might make the call.

Also, do you happen to know the wall thickness of your PVC? My small ones are .120" and my large ones are .150" and very white. I really don't know if they will be ok yet.

Grizz,

Do you happen to have a link to a picture of what you mean about glue to the bottom since I do want to keep the foil out of the roots and also I'd love to see what you do over the pot up to the stem if that is something you wouldn't mind sharing. Maybe you just mean don't lay the aluminum like we're covering a roasting turkey in a deep pan across the whole set up (several channels), but rather we should wrap/glue each channel individually?

Also, have you tried or heard of anyone successfully just using a coat of white paint or could you guess if both the black+white usually going to be required.

Looking at mine I am betting .120 ish, I will check it in a day or so. If I can remember my calipers.

Thanks Rio. If you can check it out that would be great. It would be nice to know in advance generally how thick PVC we need (if this makes sense) to block light without additional covering.

I just looked at your picture of the res in the pics you shared in the other thread. If that is the same one or design you are talking about I would try an easy thing if the algae is collecting there, without even bothering with two totes. On the return fall into the res, I would put a big paper coffee filter in the bottom of a perforated bucket and just let it run about an hour, and be around to put new filters in as they clogged up. I bet you could get rid of lots of the algae that way and even if you could turn up the flow rate, the soluble fertilizer would pass right though. If you have an extra tote bottom you could run everthing into the new clean tote until the old one was used up without missing a heartbeat, and then keep running till it cleared up, and save the fertilizer. That would work in cases you were unhappy with the algae but would rather not wait till a change.

EDIT:
On second thought, I asked the wrong question; don't worry about the thickness. It won't help knowing it for most of these channels since they will likely all need some covering. Here's why: PVC is clear and transmits light.
The manufacturers don't use a standard amount of white colorant to make the PVC we know and love, it varies, but it is usually titanium dioxide. The cheapest stuff that looks white is at about 5% TiO2. I found a formulation on line with 15% that bragged about 2 years of R&D and it let through *only* 8% of the light, a very expensive product I think about .100" thick. That basically says anything white I've looked at for PVC channels is just not going to make it. The fencepost for example has 8% I iknow from talking to the manufacturer and is made to be whiter and more expensive. No one is going to give us a free lunch with extra TiO2 they don't have to since it is way more expensive than PVC resin it gets mixed with.

Other additives could make it more opaque, but the general idea I get is that all the flat white channels will be letting around 20% of the light through, because that is the formulation that looks white enough. If they make the PVC thicker, they probably just cut back on the expensive colorant, no free lunch for us. Oh well. I should've known better!

This post was edited by PupillaCharites on Thu, Aug 22, 13 at 3:12

That's a great idea, I may work that into day to da operation. It is the same system. I am gonna change it out this weekend so I will probably just hold out till then.
Thanks for the input

I will see if I can get you something that shows what I mean.
Yes, I meant wrap each channel individually. And before you wrap them, go ahead and have the holes (to receive the net pots) drilled. Those holes will be on the top of the channels.
You basically layout a strip of aluminum foil the length of your channel. spray the bottom of the channel (opposite side from the holes) with the spray adhesinve. lay the channel top side down roughly centered on the aluminum width then pull up one side and press onto the spray adhesive. It will be facing up since the top is facing down. after that, spray the bottom with another coat of adhesive. You'll actually be spraying the aluminum you just adhered to the channel, but it is still the bottom. then wrap the remainder of the aluminum and press onto this new layer of adhesive. Then flip the channel over (so the top is up) nad cut X's at your net pot holes and fold them into the channel. I press them flush against the inside top of the channel so they don't get wet. Insert net pots with media and you're done. Well you have to block the ends, but that will depend on how you allow water in and out.
Now with all that said, I will try to post some pictures. It may take a few days though as I have to find time to take them.

Grizz, I owe to thank you for being so generous with your tips & techniques. Been so useful for me (and Rio commented too already) in thinking out these systems. My channels are ready to pick up today so as with Rio's project the timing was perfect. A pic would be great but I get how the foil is anchored inside around the hole-lip.

i used the advice ! instead of using aluminum foil, i used the aluminum duct tape, worked great !

woke up this morning to find my nutrient solution is cloudy.i have the foil tape around everything,ph is at 5.7 and ppm are 1140.did a complete nutrient change /water change on this system last night before bed.mine is and outdoor system but im absolutely positive no light is getting in now.wondering if the cloudyness could be due to the algae dying off?btw,mine is a nft system !

My nutrient has taken a day to clarify both times I have changed it.