Freshwater Habitats Trust developed PSYM (the Predictive SYstem for Multimetrics) to provide a means of assessing the quality of ponds and small lakes in England and Wales.

What is the PSYM method?

The PSYM (pronounced “sim”) method provides an assessment of the ecological quality of any pond compared to a national reference set of high quality ponds. It requires basic environmental information including pH and identification of the plant species  and invertebrate families found at the site. The survey methodology is described in the PSYM survey manual.

This method can only be validly used for sites in mainland England and Wales and the IOW.Samples need to be collected during the summer survey period (June-August). The method cannot be reliably used for ponds that are highly seasonal.

We have also developed PSYM for canals but no longer provide a canal PSYM analysis service. This is because reliable data on key predictive variables, particularly canal boat-traffic, are no longer publicly available.

Download the PSYM manual
Man pond dipping with net.

Calculating your PSYM score

Once you’ve collected your pond data, the PSYM calculation can be carried out by emailing us your data for analysis. There are two ways of doing this:

If you provide us with the plant and animal lists from your PSYM survey and allow us to add the information to the PondNet database so it is freely available for others to see, we carry out the PSYM analysis free of charge. To do this you will need to:

  • Fill out our PSYM Proforma Long 2022
  • Ensure that your sites have been surveyed with landowner permission and that there are no objections to the data being made publicly available.

Alternatively, if you do not wish to make your data public, you can fill out a Short PSYM proforma and we can still carry out the analysis. However, there is a charge of £18 plus VAT per site made for this service.

Please send PSYM data for analysis to Penny Williams: