Crystal for Beginners

Crystal for Beginners

Clearing green algae from your pond can be very rewarding. A clear sparkling pond can be a source of pride and joy in your garden. The key to achieving success with Hydra Crystal is test, treat, and Filter, Filter, Filter!

Crystal Fish

It is very important that you read all the guidelines supplied with the product before treatment. The key one being oxygen requirements for your fish. To read more about oxygen click here.

We strongly recommend conducting a preliminary glass test before applying the product to your pond. Residual chemicals can prevent the product from working, so the glass test will show us if the product is suitable for use in your pond.

Step 1. The Glass Test
  • Stir water up from the bottom to make it representative of the entire pond and take a sample of water out into a half pint glass.
  • The first check: is the water green? If it is, add a pinch of crystal to the water, just like a pinch of salt.
  • Leave the sample to stand overnight. This test will tell you if you have the right product.
  • After 24hours, what has happened to the water? If your water has cleared in the glass then proceed to the next step.

Glass Test

If the test fails and your water doesn’t clear, the product is not the right product for your pond. The minerals in Hydra Crystal have not coagulated the pond algae.

VERY IMPORTANT: Only apply the product to your pond if it clears in the glass! Your glass is your pond in miniature. If you are unsure call our customer services team.

Step 2.Treating your pond
Calculate the volume of water in your pond. Click here for our pond volume calculator.

1kg of Crystal will treat up to 10,000 litres of water. To calculate how much product you need to use, you can utilise the following equation:

No. of litres in your pond / 10,000 = X kg.

If your pond is 6ft x 10ft x 2ft = 3398 litres(using the pond calculator).
Using the above equation: 3398/10,000 = 0.34 kg or 340g.
1 level scoop of Crystal is 20g. 340/20 = 17 scoops
Treat your pond in late morning to early afternoon (why? Click here for oxygen requirements for fish)
Make into a slurry by taking a small container of TAP WATER (do not use pond water) and mixing the correct quantity of Crystal with the water. This is not an exact science, making into a slurry aids distribution throughout your pond water.

Pour into your pond at the pump outlet for maximum mixing within the pond.

Step 3. Filtering out the Algae
In order to achieve a fully clear pond the dead algae needs to be filtered out. Crystal will clump the algae together, and then it is the role of your sponges to filter these algae out.

This step relies on your filter system doing this effectively. The denser the sponges in your box, the quicker the water will clear. Our pond Filter Blanket filters down to 20 microns. This is very small! If you do not have one of our blankets, there are other options available such as Japanese matting etc. Coarse sponges that only filter out solids, gravel filters and filters without a mechanical filtration element will not be sufficient to filter out the fine, clumped, dead algae.

 Hydra Crystal Clearing
After a few hours of treatment, check that your filter is capturing the algae. You must continuously clean your filter sponges in order to remove the trapped algae.

The speed in which Crystal works will depend on the flow of water through your filter and the efficiency of your sponges to trap the fine algae particles.

Suggestion: You can cut our pond filter blanket to size and use it in place of one of the coarse sponges in your filter. This can be easily removed and cleaned throughout the treatment.

In time, after successive filter cleanings, your pond will clear.

Hydra Crystal Clearing Filter
What happens if my pond does not clear?
There are only two reasons why your pond has not cleared:
  1. You haven't used enough of the product (check dimensions and calculations – we can help you with this)
  2. You have not successfully filtered out the dead algae.

To check if the filter is adequately filtering the dead algae out of your pond water take a sample of water out of the pond and leave to stand overnight.  Does the water clear? If the water clears in the glass but still hasn’t cleared fully in the pond, this shows us that you have used the right amount of product but you haven’t filtered all the algae out. Continue to circulate the water and clean your filters, the addition of a pond filter blanket at this point if you don’t have one would be highly beneficial.

Another way of checking if your filter is trapping the algae sufficiently is to take a sample of water from the filter outlet and compare it to the sample from the pond. If there are bits/algae particles floating in the water in the sample from the outlet, we know that some of the dead algae are still getting through the filter.

Step 4. Re-treating your pond
If your pond water is very green, you may need to re-apply again. You can re-apply after 48 hours if the pond is not clearing. We suggest you conduct a partial water change of between 10-20% of the pond water between treatments.

Oxygen Requirements


Ensure Sufficient Oxygen before Treating your Pond

High air and water temperatures lower the level of dissolved oxygen present in the water. Oxygen is vital for your fish, many fish fatalities occur due to lack of oxygen. For example Koi need a minimum of 6ppm dissolved oxygen at rest and higher levels when active. Most ponds require 8-10ppm dissolved oxygen. You can only find this out is by measuring the amount of dissolved oxygen with a test kit. The best way to get oxygen into the water is via an Air pump and air stones.

During the night the algae in your pond absorbs oxygen. When the morning comes, the oxygen levels are at their lowest level. During the day the plants and algae gradually release oxygen back into the water as they photosynthesise. That is why the best time to treat with Crystal is Late Morning.

Crystal releases an ‘electric shock’ to the algae which quickly causes it to swell and clump together. Whilst this is happening, the algae are no longer releasing oxygen into the water. This is why it is so important to have adequate aeration in your pond. When removing algae, you are removing one of the sources of oxygen to your pond. 

Oxygen is the single most important element in your pond for your fish.  It is not only your fish that use the oxygen at night: algae, plants and bacteria do too. The fish get what oxygen is left.

If you see your fish coming to the surface and gulping for air, there is not enough oxygen in your water available to the fish. Whilst photosynthesis may supply enough oxygen for low fish loads, most ponds will require additional aeration which can be achieved by the huge column of bubbles created by Air Pumps. They bring oxygen depleted water at the bottom of the pond to the surface where the bubbles burst and create surface turbulence, circulation and aeration. Air Pumps can literally breathe life back into your pond.


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