Hydra Crystal (Pond Green Water Treatment)
Pack Size: 1Kg upto 10,000LPack Size: 2X1Kg upto 20,000LPack Size: 3X1Kg upto 30,000LPack Size: 4X1Kg upto 40,000L
Pack Size: 5Kg upto 50,000LPack Size: 2X5Kg upto 100,000LPack Size: 3X5Kg upto 150,000LPack Size: 20Kg upto 200,000L
Pack Size: 2x20 KgPack Size: 3x20 Kg

Hydra Crystal (Pond Green Water Treatment)

Our Price:  £20.00
List Price:  £21.00
Saving Of:  £1.00 (5%)
(Inc. 20% VAT)(£16.67 Exc. VAT)
Pack Size:

Combo: Crystal + Bio Aquatic Bacteria

For Pond/Fountain Water Volume Calculator Click Here

  (12 Reviews)
  • Clear green water in fish pond to give crystal clear water
  • Only to be used in conjunction WITH an External Filter Box with Sponges
  • Shelf life 3 years, 1 kilo treats up to 10,000 litres

Brand:  HYDRA


  • Hydra Crystal acts rapidly on the pond green water to give you crystal clear water.
  • Completely biodegradable.
  • Free of all toxic additives, mineral-based Hydra Crystal absorbs and chelates phosphates, nitrites, and other water pollutants to give you a clean healthy water body.
  • This special green water treatment formula improves the water quality without disturbing the ecological balance of the pond.
  • Safe for fish, reptiles, birds, invertebrates, mammals, humans and water plants.
  • No damaging effect on concrete surfaces or synthetic liners.
  • Not harmful to biological filters or pumps installed in the pond.
  • Immediately after the product application, scattered single-celled algae flocculate and clump together to be removed through the filter system.


Spring sunshine is a welcome change in the weather, but with the onset of warm weather, your clear pond may become green due to unsightly algal growth. The nutrient build-up over the winter months, actively feeding fish in warm weather, and along with the sun rays penetrating the pond surface, create suitable conditions for phytoplankton to thrive.

Phytoplankton or single-celled algae, make the clear pond water turn green or like pea soup.

Algal blooms are not only visually unappealing, but excessive algae also compete with fish and other aquatic creatures for dissolved oxygen during the night.

On cloudy days when single-celled algae are unable to replenish oxygen with photosynthesis, depleted oxygen levels prove harmful to the fish and other water plants.


How to Get rid of Green Water

Hydra Crystal is a unique mineral-based formulation that acts fast on the algal cells causing them to cluster together and descend to the bottom of the pond where it could be picked up by the pond filters. It is important to have the filters running and regularly cleaned during the treatment.

Hydra Crystal used in combination with Bio Aquatic Bacteriakeeps the single-celled algae from returning. Hydra Bio Aquatic Bacteria is a blend of favourable bacteria that feeds on excess nutrients (on which algae survive) and thwarts algae growth.


Usage Rates Dilution 1:10,000

  • 1 gm of Hydra Crystal treats 10 litres of water (2.2 gallons).
  • 1 kg of Hydra Crystal treats 10,000 litres of water(2,200 gallons).
  • 5 kg of Hydra Crystal treats 50,000 litres of water (11,000 gallons).
  • 20 kg of Hydra Crystal treats 200,000 litres of water (44,000 gallons).


  • Apply Hydra Crystal near the pump outlet for thorough mixing in the pond or mix with enough tap water and add as slurry to the pond

NOTE – Hydra Crystal can only to be used in conjunction WITH an External Filter Box with Sponges (fine, medium and coarse). Sponges need to be either new or in very good condition and cleaned regularly.

How to use

Mix Hydra Crystal with enough tap water to add as slurry near the pump outlet for thorough mixing in the pond.

For large bodies of waters such as lakes and large ponds, use Hydra Rapide.

Hydra Crystal will make single-cell algae clump together, and will need the filter system to clean them out, therefore a filter system is required for best results. 

During treatment ensure minimum of 8-10 mg/l DO (dissolved oxygen). Use aeration by water pump or air pump, remember blanket weed / algae is adding oxygen to your water, therefore removing it will lower your oxygen level. When treating allow plenty of time to observe fish in case of adverse reaction (increase oxygen levels in water if required).

30ml Level Spoon - Holds 24g - Treats 240 litre (52 gal)

1 g Treats 10 ltr (2.2 gal)

1 kg Treats 10,000 ltr (2,200 gal)

5 kg Treats 50,000 ltr (11,000 gal)

20 kg Treats 200,000 ltr (44,000 gal) 

NOTE - DO NOT MIX with any other product. Do not use when temperature is below 12°C (54°F). Second Application (if necessary, after 48 hours) will require a 10-20% water change before re-applying at same rate.

Best Time To Apply

As with all pond treatment products, pick the coolest time of day to apply. DO NOT USE on very hot days. Ensure your pond has adequate dissolved oxygen (8-10 mg/l dissolved oxygen). Remove any dead algae that floats to the top as it occurs.

Hydra Crystal requires an external filter to remove the treated algae. Do a glass test (see “Important Information” instruction sheet) before adding Hydra Crystal to pond. Do not use if your water does not have a green tinge as Hydra Crystal needs single cell algae to react with


Is this ok to use in soft water areas?

Yes, you can use Hydra Crystal in soft water areas.

Is it safe to use within a duck pond?

Hydra Crystal is safe to use where ducks are present within a pond.

Average Rating (12 Reviews):  
Write a Review and share your opinions!

A small pond with plants and fish ....
05 May 2021  | 

Having a really bad season with algae this year I installed a pump and UV filter, and have been dosing with Hydra Crystal treatment every 48 hours for the past 10 days.
At first there was a slight improvement, but today the water has cleared so that I can see the bottom of the pond, and the fish for the first time since last summer.
I believe this to be as a result of the filter and the Hydra treatment together. Very happy.

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1 of 1 people found this review helpful.

New Review
06 April 2021  | 

I would like to let you know that I think Crystal is the most amazing product.

I have a teeny garden pond with an external filter system.I need to replace the external box but it's not on your site.
I do find there is sludge on the floor of the pond, and also greenish water with algae, once the sun comes out, and suspended particles clouding the water. Usually stirred up by me tending to aqua plants...
When I use a scoop of Crystal and return an hour later, it`s like a miracle. The water is clear, the sediments are deposited Sadly often on my little pump, but I lift it out and clean it off.
So I have loads of frogs and their frogspawn and I can see tadpoles as they arrive.

I`m on my second bag, and I think it`s a first-rate product.

Thank you

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4 of 4 people found this review helpful.

Excellent customer service
28 May 2020  | 

Having had ongoing issues with dirty brown/green pond water, I called their customer services department and spoke to Julie Anne, who clearly knows her stuff. Helpful, patient and understanding, I followed her advice and we now have crystal clear water, probably for the first time in about 8 years. You now have a customer for life! Canít thank you enough 👍👌, 5 stars with pleasure


This review has not been appraised.

Green water treatment
05 August 2019  | 

On my first application of hydra clear green water treatment I seen a slight difference but not enough, after 24 hours tried again with a 10% water change still the same, so onvwaiting 2 days thoughtvid try again but had changed my filter sponges around 1st then instead of pouring the solution onto the pump put it all over the water including my water fall where there is a little pool at the bottom, to my surprise within 5 mins my small water fall pool was clear and after 20 mins my pond was still particles floating but I can actually see my fish even the writing on my pond pump, very happy now I will be buying this product again to keep on top of my pond water and will advertise this product and company , very happy fish mum,👍🏼👍🏼👍🏼👍🏼


28 of 28 people found this review helpful.

Green water treatment
10 July 2019  | 

Perfect just as product descibes


25 of 25 people found this review helpful.

Does what it says
30 June 2019  | 

bit cloudy , but has cleared


25 of 25 people found this review helpful.

Hydra Crystal (Green Water Treatment)
01 June 2019  | 

I recently (May) visited my relation in Cornwall and the pond I had renovated in December was totally green and they couldn't see their fish. I purchased this product and I had a phone call yesterday (2 weeks later) and they were over the moon as they can now see their fish swimming around at the bottom of their fish pond.
I have been using Hydra blanket weed products for the past few years and they are excellent.

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17 of 18 people found this review helpful.

Very pleased
11 April 2018  | 

I have been on a search for many months trying many different products to treat green water. This product really does work as I no longer have algae just crystal clear water.


7 of 7 people found this review helpful.

hydra crystal does what it says
20 April 2017  | 

Pond had horrible murky pond water found Hydra Crystal on web, placed order, product arrived next day used it in pond which is now clear within a couple of days.


6 of 6 people found this review helpful.

Highly Recommend
04 March 2017  | 

I did the glass test which was recommeded by the manufacturers where you will see remarkable results. I took 2 glasses of pond water where I treated one and left them overnight. The treated water was almost as clear as tap water, WOW. My Koi pond water is now practically crystal clear after one treatment.I would highly recommend this product.

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14 of 14 people found this review helpful.

Read all 12 customer reviews...

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