Gelatinous Zooplankton

[galleon]

How many of you would be interested in keeping a display dedicated to sea-jellies (jellyfish) or ctenophores?

Instead of explaining it all to you, lets see if I can get any takers:

How would you design a tank to keep them? You have three requirements. They cannot touch any hard objects, there can be no air used, and the flow cannot have a high velocity, as any of these would be fatal to the medusa.

[galleon]

Bear with me, a club wants me to give a talk sometime in the future, and I'm tired of talking about corals, so I'm trying to relate something a little different to the hobby.

[Spanky]

Am I allowed to play?

[galleon]

Absolutely!

...this will be interesting (winks to other TRT members).

[foobuddha]

Jellies would be great to keep, but can't be easy (or everyone would be doing it).

You need a round tank with water flow running 'parallel' to the wall to provide a current for the jellies to drift along in. Oh and no aquascaping!


I understand some people are having success keeping upside-down jellies.

[Spanky]

Looks like a horseshoe with the open end at the top. Spray bar in front of a screened overflow,circulating water across the screen and down, around, and up and over in tank.

Pelagia noctiluca are really cool cause they glow under black light and look like a lava lamp.

At least that's the way we've been doing it for years.

What'd you come up with?

[galleon]

Yep, that's the basic concept for all kreisels (German for spinning top), which are what most plankton systems (especially the gelatinous kind) are.

There are four kinds, Kreisels, circle kreisels, stretched kreisels, and what Jerel described, pseudokreisels.

Spraybar doesn't work for most species because of high velocity entrainment, It usually has to go through a secondary chamber that is larger, and then is squeezed out of that chamber by a slit the width of the tank that points down in front of the overflow screen.

[galleon]

Pseudokreisel

[galleon]

(Look at the sketch I made before you read, it may make more sense). Go through this process in your minds to help you visualize it: Take a slice of an acrylic cylinder. The cylinder slice has to be long enough to accomodate your species width-wise, and can otherwise be as long as you want. The diameter is also dependant on the species. Ctenophores can stand a 12" diameter, where as something like moon jellies need 4-6 feet of diameter. Lay the cylinder on its side. Now cap the open ends of the cylinder with a sheet of acrylic on either side. Cut off the top of the acrylic cylinder's side so you have an open top between the sheet sandwhich.

On one side, make a triangular overflow box that is the width of the acrylic cylinder slice. Cut rectangular holes in the face of the triangle and weld perorated acrylic (overflow strainer) in front of them. On the back/vertical leg of the triangle, drill 1.5 inch to two inch holes across the width. Tap them and put male adapters in. Using a hartford loop/rise (ie, an external durso), set where the water level in the kreisel will be, then drop the 2 inch to the sump.

Now, in front of this overflow triangle and above the square holes for overflow, put another triangle, smaller in volume, but still the width of the pseudokreisel. On this triangle, however, don't connect two of the legs (the ones that meet up at the bottom), leave them about a half a centimeter apart. Drill the top/horizontal leg of this triangle with your desired return line diameter (likely 1"), and with at least two return holes. The slight opening between the two triangle legs, where they don't meet up, runs the width of the kreisel and thus forced the water being pumped into the triangle to enter the tank/cylinder as a laminar sheet that is also the width of the kreisel.

This laminar sheet will travel around the inside edge of the cylinder, acting as a non-solid barrier wall that pushes the jellyfish back into the "open water" of the cylinder before they contact the wall. By having the sheet of water exit the return and travel in front of the overflow, if/as the jellyfish become entrained in the overflow suction, they are forced down/away from the screen. It usually takes significant pump power to get this roll going and maintain it, depending on the tank size, dual Iwaki 55's or even 100's are often used.

[Geoff]

why can they not touch a solid object? i know they do not encounter this in their environment, but does it do harm. i have been thinking of this for a while but lacked an info source to bounce ideas off of. i can see how these Kreisels will work for jellies like moons, boxes, and combs, but would not work for your avatar. that will have to be a different enclosure altogether.

i love engineering problems.

G~

[cyberchef]

I know that if they are placed in a container with flat sides they can get into a position where they are trying to "pulse" through the flat side, and of course go nowhere. I've also seen them upaside down trying to "pulse"/"swim" down through the bottom of the tank.

I actually thought about setting up a tank for jellyfish when I saw some for sale at a LFS. When seeing what predicaments they can get into in a regular tank I thought of a round tank. With the return designed so that it ran parralell to the walls of the tank. sort of forming a flow of water in the tank that was moving in a circle, sort of like a whirlpool but much slower.

[galleon]

why can they not touch a solid object?

Tears/destroys the bell. The tissue is very very fragile.

i can see how these Kreisels will work for jellies like moons, boxes, and combs, but would not work for your avatar.

Heheheh. My avatar is not gelatinous zooplankton or a "jellyfish", even in the most general sense of the word

[Geoff]

what about a tank within a tank. the inner tank has hundreds/thousands of little holes all over it. the outer tank is sealed around the inner tank. this is pressurized to create small water jets towards the inside of the tank. one side could be free to allow viewing. the top could be open. the larger the vessel the greater the pressure difference with the tiny holes the velocity would be great at exit but should dissipate quickly into a nice nudge towards the center. you could theoritically do this to 5 sides. it may require zones on the outside tank to keep the pressure equal around. removing the water will be a bit tricky but you could use slits in the upper corners. make them overflow boxes. may require a slighter higher pressure at the top to counter act the overflow suck.

make any sense.

G~

[mojoreef]

OK Chris think Indy 500 then think Kreisel

Mike

[galleon]

Makes sense Geoff, but constant opposing flow would be very stressful on jelly medusa.

Mikey, we could start a pool on which jelly makes it around first