Ocean Free Activa Block - Super Charged Activated Carbon Block

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Ocean Free Activa Block - Super Charged Activated Carbon Block
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Ocean Free Activa Block - Super Charged Activated Carbon Block

Ocean Free Activa Block - Super Charged Activated Carbon Block

  • Can be used in an external filer, sump or put straight into the aquarium
  • Rapid absorption of toxic pollutants, discolouration, odours and medication in your aquarium.
  • Absorption rates are equivalent to 20kg (for the 500g cube) or 10kg (for the 250g cube) of activated carbon
  • No pre-rinsing and filter-media bag required- simply place into your aquarium or sump.
  • Ideal for both freshwater and marine aquariums.

The Ocean Free ACTIVA BLOCK has to be one of the best carbon-based filtration medias available on the aquatic market. This super-charged activated carbon block is designed to maximise the absorption of aquarium water discolouration, odours, toxic pollutants (e.g. insecticides and chemicals) and medication. Ideal for all types of marine and freshwater aquaria.

Highly-porous natural bamboo activated carbon and sepiolite clay minerals are precision cut into a cuboidal matrix design, featuring 1400 micro-tunnels. This greatly increases its surface area and boosts its ability to draw out toxic pollutants from your aquarium water quickly and efficiently. As a result, one cube has the equivalent absorptive capacity as 40 times its weight of regular activated charcoal powder. Therefore, the 250g cube absorbs to the same capacity as 10kg of regular activated charcoal powder, and the 500g cube to 20kg. Absorption test results carried out by the US EPA Methylene Blue Method shows the 250g block can absorb 1mg of Methylene Blue within 3 hours. Now that’s impressive!

The OF Activa Block can be used in any aquarium or sump tank that you wish to help remove toxic pollutants/discolouration/odours/medication. The block works best in aquaria with efficient water circulation and flow. The block requires no rinsing prior to use, and it may create bubbles for the first 30 seconds after adding it to the aquarium. 

Another useful but completely different use is, it can also be used to keep fruit fresher for longer by absorbing ethylene gas – simply place in your fruit bowl and see the difference!

Small  Large
Dimensions 100 x 50 x 100 mm 100 x 100 x 100 mm
Weight 250g 500g
Treat Aquariums up to 150 L 300 L

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Delivery costs for your order will be calculated during the checkout process based on your delivery address and the contents of your basket. You will only pay one delivery charge for your order. Express delivery is FREE for online orders OVER £39 unless any of the points below become a factor.

  • Some large items like aquariums, ponds and pond liners will have an additional charge of £45.00 to help offset the cost of a pallet delivery.
  • Orders containing a physical gift card will have an additional charge of £2.45 to cover the cost of materials and delivery (digital gift cards are a free alternative).
  • Orders to highlands, islands and Northern Ireland may incur an additional delivery charge displayed at checkout this is based on the postal code provided. DPD provides a list of postal codes which have additional surcharges. Some of these post codes may also take 2 working days to arrive, even on express. Pallet deliveries cannot be sent to these post codes.

We only ship to the UK and cannot ship internationally.

We aim to dispatch items that are currently in stock on the same working day if they are ordered before 2.45 pm (excluding Bank Holidays). Orders after 3pm will be dispatched the following working day, unless it fits any of the below criteria:

  • Orders containing live plants will take up to 2 weeks to arrive. We take a week's worth of customer orders and then inform the plant farms of the specific quantities we need to fulfil that week's order to avoid wastage.
  • Pallet orders containing large items like big aquariums will take additional time to arrive as they are sent by a third party. These orders will NOT be dispatched until we have been in touch to arrange a delivery date, this is to ensure someone is available at your address to sign for the delivery. Deliveries will generally be delivered ‘curb side’ within the terms of the agreement we have with our couriers so you will need to make arrangements to transfer larger items into your home yourself. Unfortunately, our drivers are not insured to transfer the aquarium into your home.
  • Physical gift cards and items from the gift shop (such as clothes, towels etc) are sent with 1st Class Royal Mail. Delivery usually takes 1-2 working days, though in rare cases and orders placed closer to public holidays (Christmas, Father’s day, Mother’s day etc.) may be longer.


If you are not 100% satisfied with your purchase online from our website, you can return the product and get a full refund or exchange the product for another one, for up to 21 days from the date you purchased it.

We strongly suggest signing up for an account with fishkeeper.co.uk as this will allow for some additional returns options like return to your local store.

If you checkout as a guest you will need to return the product to Maidenhead Aquatics, PO Box 619, Egham, Surrey, TW20 2BS, please package the order (along with a packing slip or a note including your name, address and order number).

Large pallet items like aquariums are deemed delivered successfully with no damage once the the driver has left the property. If a report of damage is submitted after the driver has left we may be unable to assist with replacements. We recommend refusing a damaged delivery, this is the fastest resolution.

Our full terms and conditions can be found here. When you place an order with us online you are agreeing to these terms and conditions.

For delivery before Christmas, orders must be placed on or before 3pm on Wednesday 20th December. We cannot guarantee delivery of these orders pre-Christmas as we are reliant on our couriers, but will use our best endeavours to get orders placed on this date out to you before Christmas. For full details of our festive delivery and opening times click here

Please note: online orders placed after 3pm on Friday 22nd December will not be dispatched until the New Year. For full details of our festive delivery and opening times click here