Best and cheapest solution for covering top of rockwool cubes to protect from light?

Indoor Growing Hydroponics
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I did read that you should cover the top of the rockwool cubes with a sheet which does not let the light through…

I dont want to spend a lot of money. I have many cubes to cover. Also should I only cover each cube or the whole ebb and flow table at once?

I still have a roll of some blue plastic sheet here. Can I use that, or does it need to be white??? Does it need to be 100% light proof?

Actually what is the logic behind the cover? Is it because of algae growth, protection of the roots from light, less evaporation? Or is the covering not really necessary?

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I think the main purpose is algae. I’ve seen many successful rockwool grows without it, so I don’t think it’s really critical, but maybe a rockwool expert can offer some more insight.

Anything light proof should be good if you do try it.

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What is the problem with algae? Fungi?

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Algae grows on the tops. It doesn’t seem to affect anything. Once the plants grow in, the canopy mostly blocks light from the tops of the cubes anyway. It does look snazzier than green cubes I suppose. I don’t much see the point in covers, you certainly don’t need them.

Running bleach and peroxide in your reservoir will discourage algae growth.

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Just cut a piece of garbage bags and cover the cubes with it

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Light is harming the roots?

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Doesn’t seem to be a problem. Light doesn’t go very far into the rockwool cube. It’s pretty opaque.

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How far? I am using SOG with small plants and small cubes.

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Not far enough to be concerned about, the effect will be negligible.

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Check out argo945 his uses some good stuff on his drip and ebb grow.

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btw… so far I never put a cover on the top of the cubes. I think it is something that is not really needed.

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I buy a huge roll of panda film, cut my own covers to size, cheap, easy, work great and can be cut to any size/configuration.

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I’ve done with/without with no issues either way, plus my plants get so big there is little to no penetration to the cubes by the start of flower the latest. I honestly don’t think it’s a concern unless your buckets have a very short distance to the light and you can see open water through or around the rock wool . You don’t want light getting to your water but tbh on the rock wool is not an issue as when I was running ebb & flow my big ass cubes were covered in algae most times and I never noticed any adverse affects.

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I know this is a well dated thread but thought I would chip in. I used to grow all the time without covers and had no real issues. The only real impacts I am aware of are:

  1. It attracts fungus gnats. So if you had a fungus gnat infestation then having algae on top of the rockwool makes it really hard to get rid of them.

  2. Once the plant grows and shades the rockwool the algae dies off and becomes hydrophobic. If you ever top water for whatever reason the water/nutrient does not soak into the cube as well. This also makes it very hard to get rid of fungus gnats because pockets of the rockwool near the top will not get properly soaked with whatever you are using to get rid of them. So the gnats hide in those pockets.

The second point becomes a lot more of a problem if you keep the plant long term like a mother plant. After a while you sometimes have to re clone the mother to replace it because the rockwool becomes so hydrophobic on top that it becomes very hard to flush them properly. For flowering plants none of this is a problem as they finish before the algae gets too bad.