Ocean Free Hydra Internal Filter

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Ocean Free Hydra Internal Filter
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Ocean Free Hydra Internal Filter and Depurator

Ocean Free Hydra Internal Filter

  • Hydra 20 Filter, for aquariums up 100 L
  • Hydra 30 Filter, for aquariums from 100 to 200 L
  • Hydra 40 Filter, for aquariums from 200 to 500 L
  • Hydra 50 Filter, for aquariums from 500 to 800 L
  • For fresh and saltwater aquariums
  • Effectively controls nitrite and nitrate by eliminating ammonia with groundbreaking Hydro-Pure technology.
  • Simple pressure release compartments made for easy maintenance.
  • This product comes with a 2 year warranty excluding the impeller

Internal filters are an excellent alternative to large external canister filters and are perfect for small to medium-sized aquaria. They are simple and easy to set up, they sit just inside the aquarium itself meaning they can be easily installed into any fish tank, with no troublesome pipes and hoses. The Hydra Internal Filter and Depurator is no normal internal filter. Using Hydro-Pure technology that is capable of enhancing the natural filtration processes, the traditional nitrogen cycle is sped up and eliminates any risk of an ammonia spike.

Key Features:

Hydra Pure Technology
Hydro-Pure Technology is suitable for marine and freshwater fish tanks of all sizes, all types of fishes, plants and live corals including all levels of stocking density. Catapure cartridges help in the prevention of New Tank Syndrome, especially in Marine tanks application. These cartridges are perfect for any applications that require pristine water conditions with a safe and stable level of Ammonia, nitrites and nitrates acceptable for aquatic life form. The pure technology along with two charged plates in the filter wipes out ammonia particles in any aquarium eliminating the chance of a fatal spike in ammonia.

Biological and Mechanical Filtration
The filter includes a more traditional large coarse sponge. This acts as the first line of capture for larger waste particles in the water. An empty cylindrical chamber can be found in the filter and can be filled with whatever you please including small ceramic media or loose carbon.

Adjustable Flow Rate
Located towards the base of the filter is an adjustable switch to control the flow rate of the filter. This is ideal for all for fish as different species enjoy certain flow rates, marine fish and coral for example need a much higher flow rate compared with some freshwater species.

20 30 40 50
Aquarium Volume up to 100 L 100 to 200 L 200 to 500 L 500 to 800 L
Flow Rate 400 L/H 600 L/H 800 L/H 1000 L/H
Power 6 W 7.5 W 10 W 15 W
Product Dimensions 11 x 8 x 20 cm 11 x 8 x 22 cm 12 x 9 x 28 cm 12 x 9 x 30 cm
Cata-pure 1pc 1pc 2pc 2pc


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.