Maintenance-free pico design (gravity-driven)

Hi, I'd like to get some feedback on my design for an almost maintenance-free pico. I have this design set up right now in my office and it seems to work. The design is basically a gravity-driven system where clean saltwater siphons down at a controlled drip rate into the main tank. From the main tank, when the incoming water pushes the waterline above the overflow, the overflow siphon draws the excess water out into the cup, which has a bulkhead and a drain tube leading to a bucket on the floor. So, all I have to do is keep the top container filled with water, and clean water will constantly flow in, and dirty water (mixed with clean water, of course) will automatically flow out the overflow and into the bucket. In other words, this is a simple continuous water-change system. The top container is 2 liters, as is the main tank. I hope to be able to leave this system running days at a time with the only maintenance being filling up the top container and emptying out the bottom bucket. Periodically I will check to make sure that the top clean saltwater container is draining and that the drain bucket is filling up, which indicates that water is correctly flowing through and being changed from the main tank. There is no fresh-water top off. A lid (saran wrap, currently) slows evaporation. Drip rate of the incoming clean saltwater line must be faster than the evaporation rate (otherwise the waterline would never rise above the overflow and no water would ever leave the system). I plan to control salinity by periodic measurements of the main tank's salinity and corresponding adjustments of the salinity of the incoming clean saltwater. Now, as I said, I have this set up experimentally (no livestock yet) and it seems to work fine. However, I'm still a little afraid of leaving the system running unattended and coming home to water on the floor. In particular, the overflow line (an airline tube acting as a siphon) is a single point of failure. In the event that this tube loses its siphon, then incoming water would overflow the main tank and spill on the floor. Specifically my overflow is a small vial inside the main tank with a corresponding small vial outside the tank but slightly lower, with a siphon tube connecting the two. Ordinarily there will always be water inside both vials so it should be "impossible" for the siphon to ever lose its suction - unless the tank or the overflow is bumped so severely that air is allowed to enter the siphon tube. So, what I'd like to ask is - how can I prevent or make contingency plans for failure of the overflow siphon? Also, are there any other flaws or weaknesses in this design? Thanks for any feedback. I really hope that with this automated system I can again enjoy small-scale reef-keeping. My previous nano ran for a year before it crashed due to neglect. I hope that an automatic continuous-flow water change system will allow me to take proper care of my system.

 

Looks good what are you planning on keeping in the display tank?

 

Thanks for the vote of confidence For the display tank I was thinking about some "shrooms", yellow polyps, and maybe a toadstool leather. Plus a few hermits.

Do the above animals need explicit feeding, or is light enough? Again this is a pico tank, about 2 liters.

 

Interesting seamonkey!
Please upload a pic or two when you have time. I'd love to see this.

 

shrooms...not really
polyps...not really
leather...could use some phyto occasionally

crabs and etc, 2x a week or so

 

You better make sure the tube for the wastewater is clean, if not you might overflow the tank with the incoming new saltwater.

 

maybe you could put a small canister to filter the water at the bottom end and return it to the top . But could really defeat the purpose of gravity driven

 

An air-lift would be cool.

 

thats what i was tryin to think of !
thanks matt;D

 

Thanks for the suggestions. Yes, indeed, if I could find a simple way of returning the water from the bottom container back into the top, then I would have a actual sump running, which would be good. HOWEVER, one design parameter is that I don't want to spend money on extra water pumps or powerheads. I want to keep this simple. Also, I hate spending money on equipment then having it corrode and be useless later on down the line. I used to have a HOB filter I used for water movement but then I tore down the tank and let the HOB sit in the sun for a few months, and of course after that the HOB filter/pump was ruined - more money down the drain.

I really like the idea of airlifts. There are no moving mechanical parts in contact with the water, so there's really nothing to corrode or break down. Air pumps are also cheap, reliable, and can be re-used if necessary for my freshwater tank too.

I did try some brief air lift experiments to try to get the water back from the drain into the top container but failed. The air pump just couldn't push the water that far up. I have a fairly powerful dual-output air pump that I bought for about $40 (so it's not one of those wimpy $2 pumps). Even with this strong pump, the air lift tube could only lift the water about 3cm (an inch) above the waterline - no more.

My basic test was to take a piece of straight plastic tubing, stick it vertically into the water with one open end sticking up in the air, and stick an air-line from the air pump vertically down into the open end of the air lift tube as far down as possible. Feeding the air from the top results in larger bubbles and more water movement, or so I read somewhere. Then I cranked the pump to the max (it's a dual-output air pump, so I closed off one output causing the full air force to be pushed through the other output) and tested how far I could get the water to rise in the tube. An inch, or maybe 2 inches maximum, was all I could get. I certainly could not get the water to rise the ~2 feet or so needed to reach the top reservoir again.

Am I doing something wrong with my air lift? Or, did you mean using an air lift in a different way?