{"product_id":"3-inch_10cm-grodan-rockwool-blocks","title":"Grodan Rockwool Blocks 3” (7.5cm) – Small or Large Hole","description":"\u003cp\u003eGrodan Rockwool Blocks – 3\" \/ 7.5cm Starter Cubes\u003c\/p\u003e\n\u003cp\u003eGrodan’s 3-inch Rockwool Blocks are the go-to choice for growers looking to raise strong, healthy plants from seed or cutting before transplanting into their final system. Made from spun basalt rock, these clean, inert growing blocks deliver excellent air-to-water retention, consistent structure, and optimal root zone conditions for early-stage plant development.\u003c\/p\u003e\n\u003cp\u003eEach block features a pre-formed hole to fit starter plugs or rooted cuttings. Choose between:\u003c\/p\u003e\n\u003cp\u003e\u003cbr\u003e• 2.5cm (small hole) – ideal for smaller propagation plugs \u003cbr\u003e• 3.6cm (large hole) – fits larger starter cubes or root balls\u003c\/p\u003e\n\u003cp\u003eWhy Use Grodan 3\" Rockwool Blocks?\u003c\/p\u003e\n\u003cp\u003e\u003cbr\u003e• Perfect for Transplanting: Move seedlings or cuttings into these blocks before potting-on or installing in hydro systems. \u003cbr\u003e• Clean \u0026amp; Inert Medium: Free from pests, pathogens, and nutrients—fully controlled environment. \u003cbr\u003e• Uniform Structure: Promotes even root distribution and strong early growth. \u003cbr\u003e• Excellent Air \u0026amp; Water Retention: Prevents overwatering and encourages faster rooting. \u003cbr\u003e• Versatile Use: Compatible with soil, coco, and all hydroponic systems.\u003c\/p\u003e\n\u003cp\u003eHow to Prepare Rockwool\u003cbr\u003eBefore use, pre-soak the blocks for 24 hours in a mild nutrient solution (EC \u0026lt; 1.0) with a pH of 5.5. Add a small amount of root stimulator if desired to gently raise EC and support root initiation. This helps neutralise Rockwool’s natural alkalinity and primes it for plant uptake.\u003c\/p\u003e\n\u003cp\u003eIdeal For:\u003c\/p\u003e\n\u003cp\u003e\u003cbr\u003e• Seed germination and early veg \u003cbr\u003e• Cloning and cutting propagation \u003cbr\u003e• Hydroponics and soilless growing \u003cbr\u003e• Use with flood \u0026amp; drain, NFT, or dripper systems\u003c\/p\u003e\n\u003cp\u003eStart your grow the right way—clean, controlled, and consistent with Grodan Rockwool Blocks.\u003c\/p\u003e","brand":"GRODAN","offers":[{"title":"2.5cm (Small Hole) \/ Single","offer_id":39789684097208,"sku":"2528","price":0.95,"currency_code":"EUR","in_stock":true},{"title":"2.5cm (Small Hole) \/ Strip of 8","offer_id":39789684129976,"sku":"2523","price":4.95,"currency_code":"EUR","in_stock":true},{"title":"2.5cm (Small Hole) \/ Box of 384","offer_id":44413512286423,"sku":"9639","price":164.95,"currency_code":"EUR","in_stock":true},{"title":"3.6cm (Large Hole) \/ Single","offer_id":39789684195512,"sku":"2525","price":0.95,"currency_code":"EUR","in_stock":true},{"title":"3.6cm (Large Hole) \/ Strip of 8","offer_id":39789684228280,"sku":"2526","price":4.95,"currency_code":"EUR","in_stock":true},{"title":"3.6cm (Large Hole) \/ Box of 384","offer_id":39789684261048,"sku":"2527","price":164.95,"currency_code":"EUR","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0561\/9092\/7032\/files\/grow-media-3-6cm-hole-box-of-384-3-inch-7-5cm-grodan-rockwool-blocks-39901489758423.webp?v=1780155857","url":"https:\/\/www.thehydrobros.com\/de-de\/products\/3-inch_10cm-grodan-rockwool-blocks","provider":"The Hydro Bros","version":"1.0","type":"link"}