Building A Jellyfish Tank

[Lacuna]

Hi everyone,

Maybe for a first post this is jumping in at the deep end so to speak, but I'm about to build a jellyfish setup and I'd like some pointers. I know it's still somewhat of a specialist subject but I notice that jellyfish aquariums are becoming more commercially available now (there have been at least two crowdfunded companies I know of who produce jellyfish tanks and ship livestock) and I'd like to keep some small jellies. I'm about to strip out my bedroom and put down a wooden floor, all new furniture and a corner desk for me to work from, and I specifically picked out a desk which is able to support more than enough weight for the project. The jellyfish tank will essentially be for decoration but that's not to say that I'm just deciding to throw something together and pick up some fish which will be dead within a week- I've kept fish since I was about 5 and pretty much every fish I've had has outlived it's expected lifespan (15 year old goldfish still living in my pond and a 14-inch pleco raised over the past 10 years or so, to name a couple).

Now, down to the tank itself. I've been looking at Cubic's line of jellyfish setups, and as far as I can tell they're pretty overpriced. The tanks look stunning, admittedly, but their 80-litre option would run up to almost £1000 with jellies included. That's when I decided to build one myself, and with a pretty similar design. The thing is, even though I've kept fish, I've never had to put any enclosure together from scratch (I did build our pond but naturally that's pretty straightforward- dig the hole, add the store-bought filter unit, add water). With this, it's going to require a well-planned filtration system. For the enthusiasts on the forums I'm guessing this will be pretty simple, though

Aesthetically, I've designed the tank, making sure that there's enough space for the filtration system. I was just going to go for a replica of the Cubic Pulse 80, but with the design of my room I found that it would be even better to add in a front viewing port. The back isn't curved, either, as you can see below. The top, front and bottom will be made from a single sheet of acrylic, bent to shape, and then the back panel will be attached as a separate sheet. The separator panel is identical to the back panel, only it has the holes cut for the outflow. The overall dimensions are (WDH) 250mmx600mmx500mm.

Now, my questions are all around the filtration. My idea is that the water will flow out from the top of the tank and trickle down through a couple of layers of filter pads, followed by biofilter substrate/media. It will then be pumped back up to the top of the tank, and ejected through a spray bar angled to push the jellies away from the filter intake (which is covered by a sponge screen) and back around the tank. I will be using a pump with variable flow to regulate the current. The planned flow is mapped below:

The main issue is- how exactly would I create the filtration system? Could the outflow simply run down an acrylic box containing the filter pads and substrate, and then up a tube, through a pump and out the spray bar? Or is there more to it than I am thinking? I'd like to keep the cost down as much as possible with this build but if extras are essential then it's no problem, I'd just rather know the best way to do this! Thanks in advance for any replies, and again I must stress my issues are with the actual creation of the filter system so if you can give me any pointers on how I might set up the filter then I'd love to hear them.

Thanks!

 

[Lacuna]

Quick update:

I just threw the original model together to get a better idea of dimensions. I spent a little more time creating a physical render to show what it will look like when finished. I added a curved screen and an additional surface to better control the current direction. There is also a ceiling hatch for feeding and cleaning access, along with posts to keep the side panel in place (which can be removed to access the filter for maintenance).

I am now thinking of using a simple internal filter with an adjustable flow rate so I can keep the current as low as possible. I think I will use either an Eheim Pick-Up Internal Filter 2010 or an Aquael Internal UV Filter 500 with a custom-build spray bar. I think these are good choices but if anyone has other suggestions I could use that would be much appreciated.

 

[Lacuna]

Quick update:

I spent some more time thinking about the filtration system and realised that I was making it seem like a bigger issue than it actually is. I will be using filter pads behind the screen to prevent food entering the outflow. The back section of the tank is now split into 2 sections- top (water) and bottom (lighting). The section with the water will essentially be a trough containing bioballs, from which the water will travel through an internal filter before being circulated back to the main tank via the spraybar at the top. The spraybar will be level with the top of the water so that no air bubbles are introduced to the tank (essential for jellyfish).

I changed the seamless top-front-bottom panel into 3 separate panels to make construction easier. I ordered all of the acrylic today, along with tools (heat gun, solvent syringe), solvents, sealant, filter, tubing, and a remote controlled LED light (I need more clear acrylic to create a window for this light, it will shine through from the back of the tank to the main compartment). Everything is arriving tomorrow, apart from that extra acrylic which I will likely order for delivery the following day.

I am using acrylic cement to bond the pieces, and then covering every single edge with fish-friendly sealant. This will keep everything 100% watertight and will protect the jellies.

I will be starting a build log in case anybody is interested in seeing how this turns out. It will certainly be an interesting experiment, and hopefully I'll be able to show that you don't need to splash out on a fancy tank to keep jellyfish. After going over some considerations related to the requirements of the jellyfish, I am confident that this design is going to provide all of the ideal conditions for the jellies. Water salinity must also be taken into account but I will report on this separately from the tank. Right now I am focusing on building the tank itself and achieving the desired water flow.

 

[twitchy]

I can promise I'm nowhere near qualified to give advice, but I would think if you had the same amount of water going through the screen, down the overflow/intake and back out the spray bar above the screen, that the water would just go back down the intake and you wouldn't get a circular flow around the whole tank.
I would think the spray bar would be pointed away from the overflow/intake going for a counterclockwise flow around the tank. Not sure how the commercial tanks work.

Hopefully someone more knowledgeable will jump in here, but good luck! Will be an interesting build

 

[Lacuna]

I can promise I'm nowhere near qualified to give advice, but I would think if you had the same amount of water going through the screen, down the overflow/intake and back out the spray bar above the screen, that the water would just go back down the intake and you wouldn't get a circular flow around the whole tank.
I would think the spray bar would be pointed away from the overflow/intake going for a counterclockwise flow around the tank. Not sure how the commercial tanks work.

Hopefully someone more knowledgeable will jump in here, but good luck! Will be an interesting build

Hey

I also had a couple of concerns around the water flow but this is how I've seen it done with most DIY Kreisel tanks. I believe that a certain range of flowrates for the filter will result in the circular motion, it's just about balancing it where it's not too strong for the jellies but also provides enough force to kick the water around the tank. The outflow itself isn't a pipe, it's around 10cmx8cm and this flows into the back section of the tank. The large surface area (in comparison with a small pipe which would be used for a regular intake) should mean that the water entering the back section will be more dispersed than the water leaving the spraybar. In other words, even though the rate going into the filter is of course equal to the rate leaving the filter, the difference in surface areas between them should result in a higher pressure down than into the filter.

If, on the other hand, it turns out that the current isn't flowing as expected, I have 4m of aquarium tubing so it would be easy enough to discretely run another line leaving the filter down to the bottom of the tank, so there are two spraybars which work together to create the circular flow (since the filter is submerged there's no risk of air bubbles from the bottom so it would be safe for the jellies). Coupling this with a slightly increased flowrate, I'm sure that would solve any flow issues if there are any. Thanks for leaving your thoughts on this- I'm not sure when I'll have the tank finished but I'll post back when I fill it and test out the flow. Fingers crossed it works with just the single spraybar in the meantime

 

[twitchy]

Makes sense, enjoy the project!

 

[Acrylics]

I wouldn't add a supplemental jet. It'll increase suction on the screen and you'll end up with animals pancaked onto it.

I wouldn't say it's about balance on the flow rate to create the gyre as any flow rate will do so, it's more about keeping the flow rate low enough to not get pancaked animals. The higher the flow rate, the more suction on the screen - more animals stuck.

Personally, I would get rid of the curved screen and use a straight screen with your water flow running parallel to it. It's not the screen that determines the circular flow.. If the screen determines flow, then for it to do so - you'd have to be pointing the flow *at* the screen, which will just be pushing animals into the suction screen which will,again, pancake animals.

When you get it built, try using the "fold and close" sandwich baggies to help get your flow rate set. It's about the best trick I know for such things.

HTH,
James