Hey Everyone, I have been growing in RDWC for some time and learned to avoid Pythium issues after one bad bout. I have been studying Snype's RDWC methods and decided to attempt to duplicate his method/result. I built his take on RDWC and a flood table. I started my first run with clones from a local clone producer. Unfortunately all that was available were clones in soil so I had to gently wash the soil from the roots and transfer them into netpots with hydroton. I placed the clones in the Ebb & Flow table. All was looking good until I noticed discoloration on the roots of two of the plants. On closer examination I found grit/fines from the hydroton stuck to the roots. I thought "no problem". I just moved the plants from the Ebb & Flow to the RDWC system. The discolored roots looked worse and when I tried to wipe away the hydroton fines I found that there was some rot. The affected plants had been at the far end of the flood tray. I cycled the flood cycle and saw that a small amount of nutes were left in the end of the tray after drain. I am afraid that as the roots on the affected plants got long enough to reach the bottom of the tray that they landed in small puddles of nute solution. The affected plants had 50-75% of the roots unaffected and the balance of the plants have nice white roots. I dosed the RDWC system with a strong dose of H2O2. I cut as much of the affected roots away as I was able. I then drained & refilled the system and added .5ml Chlorine (to 28 gallons). I am hopeful that this will resolve the issue. Any suggestions or other input would be greatly appreciated. The pythium developing in the Ebb & flow system surprised me. How do you prevent this? BTW: My nute temps are running 67-70F and I have 4 air stones in the nute tank. Thanks FJ
Yes. Been there done that. I found that proper draining is a huge factor in a good E&F system. The drain needs to be the lowest point in the table and the table needs to be slightly tilted towards the fill/drain side (unless you have a table with the fill/drain in the center, and then the table needs to be perfectly level). I use a 3 ft carpenter's level to set up a flood table. You can't trust measuring from the floor. I have res temps get in the upper 70's and low 80's without any problems with healthy roots, and I don't use air pumps or air stones at all. I find that quick floods and quick drains is all it takes to keep the roots healthy. I found that it's better just to trim away unhealthy root ends than to treat them with H2O2 and take a chance of it moving farther up the roots. I've done root trimming on vegging plants lots of times (as a matter of maintenance with mother plants), and roots grow back very quickly after getting a hair cut.
Thank you for the reply! I did level the tray when I set it up. Yesterday I was tinkering with it and found that the bottom of the tray has warped a bit and created a low spot where water puddles. If I raise that end of the tray enough to drain then water puddles at the other end. This tray served me well at my prior location but apparently was damaged in the move. Looks like it is time for a new flood tray Thank you for the tip on trimming the roots. I was a bit fearful of doing that. I did trim the worst offenders. I do have some roots with small spots of discoloration part way down the root. I would be cutting a significant amount of healthy root if I cut above the small discolored spots. Do you think I should leave them alone? The problem is not getting worse as far as any spread of visible pythium but the plants are just a little bit droopy. Not bad but noticeable. I am planning on flushing and refilling the nutes again today. Thanks again. FJ.
Do you use a stand that supports your table on the outside using the upper lip of the table to hold it up? I found out the hard way that supporting a table by the upper lip is a bad idea. Not only will the bottom sag under weight when it's flooded, it will eventuall crack somewhere. I always support my tables now from underneath. I have one stand holding 2 3x3 tables that I could literally use as a scaffold and walk around on it if the flood tables weren't sitting on it. I used lengths of angle steel shelving material screwed to 2x4s to keep them straight. I only have legs on each end, with clear access to the space underneath.
I was using a stand that supported the bottom. But not the entire bottom. After moving it did not quite fit the same. I think the damage was done wile it was in storage.
You should be able to get the table to flatten out under weight if it's sitting on a flat surface. If the frame supports the bottom, just adding a piece of plywood on top the frame would help keep the bottom of the table from flexing as it fills and drains. You can also glue and screw some 2x2 (or even 1x1) wood strips to the under side of the plywood to make it more rigid. There's quite a bit of weight in a table when it's flooded to hold it down flat if it's on a flat surface.