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Helobdella Europaea

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Hello All! 

I am looking for a knowledge dump on Helobdella europaea. I have read the only two scholarly articles I could find on them but need a lot more information. 

One, are they friend or foe? 
Two, are they dangerous to fish (seems like no)
Three, are they dangerous to mystery snails? 
Are they dangerous to shrimp/crayfish? 
Are they dangerous to goldfish older then 3 months old? 

I have been doing some experiments with mine, I can confirm they absolutely pray on ramshorn and pond snails. But on mystery snails they appear to just sit on their shells? Are they not interested in biting they mystery snails? will they harm my goldfish? 


any information at all would be GREATLY appreciated. Thanks! The photo below is the actually leech I pulled from my aquarium (my photo) but I have since found more. 1013676040_leechinaquarium.jpg.1f6ae2c0fe13f291af96332310b475a4.jpg

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I assume the two articles you are referring to are this one and then this one. Itmay be that no one has seriously studied or published on the relation between tis leech and ornamental fish.

Here is a short webpage that covers the relationship of Helobdella europaea to tropical fish down near the end.

Common name is "European Flat Leech," and generally, it seems the answer is: "No it will not harm your fish." They seem to go for smaller things to eat -- mystery snails are probably not a preferred meal. 

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@Fish Folk thanks for the reply! I had found that website also, I am curious to see if they will survive my winter temps in my basement which online is looking like yes, and I have been experimenting with them since I have them I isolated them. 

they are 100% dangerous to pest snails, I threw a few different types of pest snails in and the mother leech at them. 

they keep their babies attached to their bellies, if the babies fall off, they re-find the mother and stay on their belly (I have a video of this) 

They do not appear to hurt the mystery snails but have some sort of relationship to the shell. I am not sure if some sort of micro organism grows on mystery snail shells (I heard they are sometimes referred to as infusoria snails, maybe thats the link?) I have seen the european flat leeches attaching their foot to the operculum of the mystery snails and waving their heads around, or just parking along the shell. 

I have them in two of the breeding tubs of my goldfish fry unintentionally, they do not appear to injury the fry at all, but I am not sure they are goldfish egg safe. 

They do not appear to eat left over food, but I am not 100% sure about that, they just didn't do it in the small container I have them isolated in. 

They HATE melafix. It does not kill them, but they do this weird waving maneuver or race to the top of the tank shortly after adding melafix, that might be a useful trick to reduce population but not all raced to the top, only about 75% of the ones I had in the tub did, the others did the weird waiving maneuver. 

Sorry for the long post, I just wanted to share what I learned since making this post. 

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