My Parospromenus

Teu­nis wrote: I was order­ing some glass worms, and came up whit some questions…

Glass worms (Chaoborus or Chorethra, “weiße Mück­en­lar­ven”) are a very good food for big­ger grown and adult Paros. Fed by them, they reli­ably get fer­tile (which often could be a prob­lem, espe­cially if fed by Daph­nia).

But I should point out that two good Ger­man breed­ers dur­ing the last years had severe prob­lems with glass­worms from the trade. One of them lost his com­plete stocks of more than ten species of Paros and many grow­ing off­spring. Among them were extremely valu­able fish that he had caught him­self at the orig­i­nal sites, so surely been deter­mined as the species known from there. The other friend lost the major­ity of his whole stock and off­spring. There are indi­ca­tions that much more peo­ple made that expe­ri­ence but up to the present day do not real­ize what hap­pens, what the cause has been.

And what was the cause of that losses? Quite clearly and with­out any doubt a con­t­a­m­i­na­tion of the com­mer­cially har­vested and stored glass­worms; in both cases there was a def­i­nite proof of this. One should espe­cially be warned against those small plas­tic envelopes which are sold in thou­sands with mostly an unclear ori­gin. The glass­worms inside obvi­ously are treated by a heavy poi­son to make them more sta­bile in that small con­tain­ers. Often some die and to pre­vent the oth­ers from being infected those poi­sons are used. Often this works well, as it seems, but there can be most cat­a­strophic results for the fish fed by them. At any rate if you can­not catch your glass­worms your­self from the next fish-​free pool (what is best) you should keep them for quite a time in a big con­tainer with much new water; best is to net them and give them with­out old pol­luted water into it.

Peter Finke