Temp outside the Grobo

Hi mate, ain’t that what you use on cuts? How much of it do I need to pour in?

@vegetato does it need to be pure Hydrogen Peroxide?

I used the 3% or 6% stuff from pharmacy. There’s also horticultural grade which is more concentrated at 20-35% which is better if you can get your hands on it. Zerotol HC is one of the more popular ones to get.

This is what I’ve done in the past to deal with this:

  1. Put some h2o2 and water in a bowl or bucket; roughly a cup of (3-6%) h2o2 to a few cups of water. If the h2o2 is only 3% it doesn’t hurt to use a bit more.

    • The container doesn’t have to be much bigger than to hold the roots and cocopod area, a large cooking pot or small pail works.
  2. Bring the whole lid with plant over to the h2o2 solution to dunk/rinse them off.

    • Even the cocopod could be host to the root rot so I kill anything in there by dunking it in too.
    • Also wipe down the lid really well.
  3. After the roots have been cleaned off, replace the dirty water with clean water.

  4. Rinse the roots off in the clean water, then replace that rinse water with clean water again to let them sit for a minute while the rest of the unit is cleaned similarly.

  5. Perform the cleaning procedure for the unit, get rid of any infection that might be looming in the reservoir.

    • Don’t forget to unplug your bottles at the front (and move them out of harms way), just take the caps off and cover them with tin foil or something to keep dust out if you don’t have the original caps. This is important to do while cleaning, so they don’t dispense or get splashed
    • Also don’t forget to remove your probes from the res while cleaning. This is a good time to do a calibration, or at least to also clean your probes. Most people put them in some distilled water in ziploc bags.

These days I just “bomb” it with a large dose of something like hydroguard until it goes away. When I catch it early enough (slight smudge on a strand of root) that works to deal with it, but it might help to do a deep cleaning first if it’s already getting bad.


:joy: :joy: :joy:


@vegetato Thanks for that, I’ll see what I can do. I live in England and Grobo don’t sell half the stuff I need to the UK. (Which I’ve found out after I got the Grobo) so I can’t get the PH Cal kit. Do you recommend another one I might be able to get over here?

@vegetato Sorted, got myself some 6% h2o2, cleaned the roots a few times until they were nice and white again. The cleaned Grobo, rinsed the water 3 times so everything is looking good again. Hydroguard should come this week so will use that too when it gets here.


You need a ph 4.0 and 7.0 to calibrate the pH probe (at bare minimum,) and it wouldn’t hurt to get the tools/paste to clean the EC sensor in addition to that.

Here’s some amazon uk links I found on a quick search, didn’t look for best price just the right product:

Full kit (has pH + EC):

pH Care kit:

EC care kit:

Hope that helps!


@vegetato Top Man, I found the same one they sell at Grobo so ordered that, thanks :facepunch:t2:


@vegetato I couldn’t get hold of Hydroguard sold out everywhere so got Great White, is that alright?

Did you get the powder or the liquid (Orca)?

The powder one is all they had.

That’s a bit trickier to use, the liquid version of that (Orca) is a more precise, less hazardous to handle (should wear a mask with powder, avoid kicking up dust, cleanup area well afterward), and less mess (FYI).

When I’ve used it (recently) the process was to add 1/8th of a gram or less to 20-50mL of water and then stir/mix it really well and then dump into the reservoir.

It helps to let the sediment settle and then pour it carefully to avoid dumping the “gunk” into the reservoir, or use a syringe or pipette to extract from the top of the mixed solution.


@vegetato Hi Mate, I just added under a 1/4 of a tsp to the water and mixed it in. It says mix 1 scoop (tsp) to 10 gallon. We have about just under 2 gallons in Grobo don’t we? :see_no_evil:

I topped the plant and cut couple of leaves from under off too.

This is what my plant look like now. What you thinking? Honestly is the best policy with me.


That should be more than enough, about half of that is what I use. It’s expensive stuff and there’s no need to waste it! It might also mess with nutrients/pH if it’s too concentrated.

My GW didn’t come with a scoop in it so I went with per-gram measurements.

Something to keep in mind is that our reservoir is smaller than the typical reservoir, and as such a lot of “recommended dosages” on labels might not scale down as effectively as the manufacturer would like. It’s better to err on side of caution and use less (chop their recommendation down to 1/2 or 1/4), only adding more if you see a need to.

What I did to come up with a good dosage for myself was calculate how much great white came out to about the same strength as the hydroguard in the bottle (at least in terms of quantity of bacillus amyloliquefaciens).

Hydroguard contains 10,000 CFU per mL, so when we add 5mL to our res that means the reservoir should have about 50,000 CFU.

By instead adding 1/8th of a gram of great white, that should be something like 65,625 CFU (525,000 divided by 8). One thing to note is that some of it won’t actually make it into the water and stays stuck to the powder (the gunky sediment we don’t add to reservoir), so that’s why I overshoot to 1/8th instead of going down to 1/10th.

Adding too much GW just leaves behind more stuff to clean up I’ve found. It helps to mix it outside of the reservoir, then just dump the liquid in but not the leftover powder/sediment/gunk. I mix it with 50-250mL of water separately first.

Doesn’t look happy yet but if you’re just adding GW now it could take a few days to see any results. I wouldn’t cut any leaves until they’re all more perky, the slouching leaves are a sign she’s not feeling 100%. If some leaves were going brown and you cut them off without fixing the issue (that was causing her to do this in first place) she’ll just start to sap nutrients from the next set up as you took away the ones she was using for food.


@vegetato, Wicked, thanks a lot for the help. I’ll keep an eye on her. She’s been through a bit of a rough time lately with moving 3 times, been in cold conditions, having tap water, having her roots cleaned, not being in the right recipe the lot so I thinks she doing alright to even be alive to be fair. Hopefully now with your help she will start feeling better over the next week. I’ll keep you updated in a few days :+1:t2::facepunch:t2:


Doing great considering all that!


Hi @vegetato, ok so I think she’s on the road to recovery. Been a couple days now and she’s changed quite a bit. Looking a lot stronger now. I was thinking of doing another h2o2 dip when I do my next water change, what you think?

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h2o2 will kill off the GW, so I’d probably recommend against doing that unless things start going south again.

I’d just keep adding some GW with each drain/fill for now. After about 3-4 weeks it might be possible to stop adding it as (I believe) there will be enough hanging around in the res between fills at that point. If you notice her slouching or find the roots being attacked again maybe do the h2o2 and re-apply GW but only if things aren’t going well.

You can also mix and pour a bit of GW into the coco pod, as that’s where it’s actually intended to go. By just adding it to the water some will splash into the dry area above the water line (roots, walls, lid) and that’s where it’ll grow but by adding it directly to the pod you can get a higher concentration in there faster.


@vegetato Ok mate, thanks :pray:t2:

@vegetato She’s defo feeling better now, she’s got loads bigger over the last few days. You can see were I topped her and now she’s growing well. There is a bit of discolouration on some of the leaves but that was from when she was on death bed before. Not sure if the roots look to good though, what you think? There are a lot more roots now.