Wednesday, March 7, 2012

Mysterious Jellyfish Death

I finally got a 200 gallon tank set up for my cannonball jellyfish. I acclimated them and introduced them. And then something weird happened. They began to slow down and eventually stopped moving. At first I though this was due to the cold, but they eventually stopped all movement. So I rushed them to my heated 30 gallon saltwater tank. They began to slowly pulse again, and eventually at full pulse. But that tank was much higher in salinity. So I used the remaining amount of my salt to make some water for them. That wasn't quite enough so I gathered a gallon jug of the strange 200 gallon tank water and syphoned it down drip by drip. For a  while the jellies were fine, but the next morning they were far dead. The water was heated that night as well. I am absolutely stumped as to what happened. The salinity was dead on. the temperature was lower than room temp but still at or higher than the temperature of the water that I caught these jellies in. I tested a spider crab and a snail as well. The crab went limp but recovered to full health when put in my good aquarium. The snail shot back in its shell but also recovered when put in my good tank. Does anyone know what might be happening?

  • The tank is a plastic holding tank, and was washed thoroughly before use
  • The water is tap but has been treated with ammo lock.
  • The salt is solar salt. 
  • salinity was proper. 
  • Temperature was a little low, but was still in range of water that the jellies were found in.
  • Water affects snails, jellyfish and crabs alike.
Is it possibly the use of tap water? Any help would be greatly appreciated. 

Also, here is some underwater footage of the jellies before they began to act up. 


  1. I'd say that tap water has a lot to do with it... our water here has all kinds of crazy chemicals so most people don't even drink it without filtration. They say you ought to only use distilled or reverse-osmosis filtered water when mixing your own saltwater.

    Also, did you cycle the tank for a while first?

  2. I thought about that too. What stumbles me is that the test snails and crabs came from a tank of tap water as well. And the jellyfish reacted better in the tap water of the good aquarium. So I'm thinking it has to be the salt or the cold.

    I also did cycle the tank. I used some bacteria from my other aquariums to help speed the cycle as well.

    I do need a reverse osmosis filter too, I never feel good about using tap water, i just need some more extra money.

  3. On jellyfishart it says you need reverse omosis water.

  4. My guess would be the water as well. Especially with 200 gallons of it. Your other tank was only 30 gallons, and while you might have made it with tap water, it probably had plenty of time for most of the extra stuff to be filtered out. Tap water has tons of chemicals in it. And with how delicate jellies are, any addition would probably be detrimental to them. Sorry to hear this bad news.

    1. Perhaps it is the tap water. I guess I need to invest in a reverse osmosis kit.

  5. I assume you have a water pump of some kind. Have you tested for electric voltage? Get a volt meter put the black probe in the GROUND hole of a three prong outlet or other suitable ground. Then put the red probe in the tank with the meter on its most sensitive setting. It will then give a reading. Of course you want a near zero reading. If you have stray voltage you need a ground probe. I think this is more likley than tap water,I've set up beautiful reef aquariums with tap water. I'm also assuming "solar salt" is aquarium salt. Voltage would explain why it affected everything. You can learn more in Martin Moe's Marine Aquarium Handbook from green turtle press.Good luck.