GROW!T Coco Caps, 4", Pack of 10

Stop Light From Turning Your Rockwool Green

Light hitting the exposed surface of a rockwool block does more than just warm it up — it gives algae exactly the conditions it needs to take hold, competing with your plants for nutrients and turning a clean block into a slimy one.

GROW!T Coco Caps are a simple, purpose-made fix. Sized to slip directly over a 4" rockwool block, they cover the exposed surface and block the light that algae depends on to grow — all without the bulk or waste of disposable plastic covers.

Reusable from one grow to the next, they're a small add-on that solves a problem most growers don't notice until it's already a slippery green mess.

Key Features & Benefits

• Sized for 4" rockwool blocks — slips directly over the block's surface for a clean, snug fit without trimming or guesswork.
• Blocks light from reaching the block surface — removes the light source that algae needs to establish and spread on exposed rockwool.
• Reusable alternative to plastic covers — cuts down on single-use waste while doing the same light-blocking job grow after grow.
• Simple slip-on installation — fits over the block by hand, with no tools, trimming, or extra steps required.
• Sold in packs of 10 — covers a full tray or bench of blocks from a single purchase, with extras on hand for future runs.
• Compact, low-profile design — stays out of the way of stems and leaves while still fully covering the block surface beneath.

Who Should Use These Coco Caps

These caps suit any grower running 4" rockwool blocks who's dealt with algae forming on exposed surfaces — especially in brighter rooms or longer light cycles where that exposed rockwool gets more direct light than it can handle without a cover.

Keeping Algae From Getting a Foothold

Slip a cap over each 4" block as soon as it's placed in your tray or system, before algae has any chance to establish — it's far easier to keep a clean block clean than to treat one that's already turned green. Rinse and reuse the caps between grows to keep them doing their job run after run.

Frequently Asked Questions

How do these caps actually prevent algae?

Algae needs light to grow, and these caps cover the exposed surface of the rockwool block, blocking that light from reaching it in the first place.

Will these fit my 4" blocks properly?

They're sized specifically for 4" rockwool blocks — check your block size before ordering if you're using a different size in your setup.

Can I reuse them between grows?

Yes — they're designed as a reusable alternative to disposable plastic covers, so you can rinse them off and use them again on your next run.

How many come in a pack?

Each pack includes 10 caps, enough to cover a full tray or small bench of blocks in one purchase.

Do I need any tools to install them?

No — they're designed to slip directly over the block by hand, with no trimming, cutting, or tools required.