Green Algae in Fish Ponds. How to Control Murky Pond Water

Tom sent this email to me and it is very typical of many emails I receive since Tom's problem is a very common one in the pond keeping world.

Hello, Tony, I just spent the better part of an evening on your site and I am very impressed- especially by your “biostraw” invention. I am an American assigned to the Netherlands and have two ponds in my garden. I have a Hozelock 7000 filter in my larger pond which is 13,500 liters and looks like pea soup. I noticed that the biomedia only fills about 40% of the bottom chamber. Am I correct in assuming (based on your hypothesis) that I could fill the remainder of the chamber with additional biomedia, plastic straws, etc. and it would be more effective?

I would like to order your book, but do not want to download it. Can I order it in hardcopy? If not, I will download. I lost two 80cm Sturgeon over the last month and it broke my heart!! I am now going to become an expert on ponds and Sturgeon before I replace them.

Thank you for your great site!!

Tom (from Netherlands)

Here's My Reply

Hi, Tom

Many thanks for the email and praise ... much appreciated

The first thing to bear in mind is that any biofilter might help to reduce green algae blooms but in itself the biofilter will NOT clear green water ... the algae cells are just too small to be taken out by any biofilter.

There are 2 solutions to the green water problem you have:

1. Install a correctly sized UV light. These work 100% of the time so long as correctly sized and maintained ... light MUST be changed every 8000 hrs or so. Also the quartz tube may have to be cleaned occasionally. You can learn about UV (ultra violet light clarifiers) here. Your 13,500 litres pond will need at least a 30 Watts UV to clear the algae.

2. You can use Viresco as an additive ... see all about Viresco available direct from UK. This is a superb natural product which removes algae and blanketweed. You don't have a blanketweed problem

You cannot have too much biomedia in your filter and I would suggest you add as much as you can. Remember to backwash the filter occasionally to remove debris that builds up. Its a good idea to place your biomedia into those plastic string bags used to pack fruit or potatoes (or at least as used in my country). In this way you can remove the biomedia in one go and clean off using POND WATER... if you cannot backwash.

My book is only available by download.

Tony