The Accidental Breeder: Assassin Snailson October 13th, 2010 at 8:00 am
The existence of a few pond snails in my tanks generally does not bother me. I figure, they perform some useful functions by cleaning up debris and eating some of the algae growth. A couple of weeks after I set up my 20 gallon tall tank, however, I had an outbreak of pond and ramshorn snails even I couldn’t stand. The little buggers seemed to be sliming their way over every surface I looked at and hundreds more were waiting to be born in little jelly-like sacks deposited on Java fern leaves. I decided I needed to take action. Pea puffers and copper treatments were both out due to the colony of red cherry shrimp inhabiting the tank. I needed an alternative. I had heard of a snail that hunted and ate other snails commonly called the assassin snail. I read the scant information I could find online and decided to give them a try. Little did I know I would end up accidentally breeding them.
I set the tank up around June 2010 and added one assassin snail August 15th. The tank’s other inhabitants include a somewhat motley assortment of mini moth catfish, Kuhli loaches, Celebes rainbow fish, and red cherry shrimp. It is fairly well-planted with Java ferns, Christmas moss, sunset hygro, bolbitis, and another durable stem plant whose name I’ve forgotten, and includes a few pieces of bogwood. The substrate is Flourite black sand. Filtration is with a HOB filter, in which I keep a few pieces of cuttlebone for minerals for the shrimp; pH is generally neutral at around 7.2. After I added the assassin snail, she pretty much disappeared for a few days. I wondered a few times if she had died, but I started to see empty snail shells here and there, so it seemed like the tragedy I planned for them was indeed happening. Soon I discovered that the assassin snail spends quite a bit of time burrowed into the sand near pieces of driftwood, with only the top of the distinctive, striped shell visible.
Little by little, my pond and ramshorn snail populations dwindled, more and more empty shells appeared, and every so often I would get a glimpse of the assassin snail trucking across the substrate or a piece of bog wood. On October 3, however, I was treated to a surprise I hadn’t read about very much when researching assassin snails: baby assassins! I was doing some tank maintenance, changing the water, trimming the plants and cleaning the sand when I spied an extraordinarily tiny version of that distinctive, striped shell half-burrowed in the substrate (center of photo).
I looked around the tank more closely and counted one… two… three… four (!) teeny, tiny, baby assassins. They varied quite widely in size, with the first that I discovered in the sand being the largest. It seems to me that this could mean they were born at different times, and so are not hatched out of blobs of slime with lots of brothers, as are pond snails. I snapped a few photos of them, trying to get them next to the red cherry shrimp, for size perspective. I did not get a photo of the very smallest one, as it was in a very inconvenient spot in the back of the tank.
One of the characteristics of assassin snails I had read about, besides the fact that they eat pest-snails, that made me want to try them is their slow reproduction rate. I am not sure that four babies in a month and a half is exactly “slow”, but I guess it definitely is when you compare it to the reproduction rates of pond snails. And, since they are so useful I don’t think I will have much trouble re-homing them if their population grows to more than I want to have. What has been the most interesting to me about this experience is that I started with only one snail. I had read that, unlike pond snails, assassin snails have separate sexes, so you need a male and female for them to reproduce. Does this mean that a female can breed one time and keep reproducing for some time into the future? If so, for how long? And, are these snails born live, or do they hatch from eggs? I haven’t seen any eggs in the tank, and if there were any, I would think the loaches might snack on them. But maybe not.
Overall, the assassin snail has been a fascinating and useful addition to my tank. The pond and ramshorn population has dwindled to almost none, and since I feed a lot of frozen blood worms and brine shrimp, I think I will be able to sustain a little colony of them.
For one last interesting point, I wanted to include a photo of a red cherry shrimp picking “stuff” off of an assassin snail’s shell. This seems to somewhat preclude any ideas that assassins will hunt adult shrimp. I see the snails and shrimp interacting close together very commonly in my tanks and have never seen an assassin eating a shrimp (I have two assassins in my ten gallon—I wonder how many babies are in there?). Also, my red cherry shrimp population does not seem to be hurting whatsoever with the addition of the assassins.
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