The Stream Doctor

April 12th, 2004

Email YOUR Questions directly to the Stream Doctor. This is your opportunity to get an experts professional opinion on anything stream related.

Q. What solution can I use to preserve nymphs and adult insects? Art Flick used distilled water and formaldehyde, but I don't think I can buy formaldehyde. I am presently using "isopropyl alcohol," but I know that is not a good preservative. John Kosick

A. The most commonly used preservative for aquatic insects is 80% ethanol. This does a pretty good job for long-term storage, although some folks add 1% Ionol, an antioxidant that helps preserve color.

Another preservative widely used by aquatic insect collectors is Kahle's fluid. It is made up of ethyl alcohol (15 parts by volume), formalin (6 parts), glacial acetic acid (1 part), and distilled water (30 parts). The benefit of Kahle's fluid is that it penetrates tissues rapidly before decomposition begins, kills quickly, and preserves color well. However, the Kahle's fluid should be drained before permanent storage in 80% ethanol.

All-in-all, I'd recommend sticking with 80% ethanol.

If you have a question, please feel free to contact me.
~ C. E. (Bert) Cushing, aka Streamdoctor
105 W. Cherokee Dr.
Estes Park, CO 80517
Phone: 970-577-1584

The 'Stream Doctor' is a retired professional stream ecologist and author, now living in the West and spending way too much time fly-fishing. You are invited to submit questions relating to anything stream related directly to him for use in this Q & A Feature at

If you would like to comment on this or any other article please feel free to post your views on the FAOL Bulletin Board!

Previous Stream Doctor Columns

[ HOME ]

[ Search ] [ Contact FAOL ] [ Media Kit ] © Notice