Large water changes (> 50%) OK on regular basis?

This used to be known as a "self-levelling siphon", where a small hole in the top of the loop set the drain level and a constant stream of water could be added to the tank without overflowing it.

Came in handy for "open range" systems that spread water from the tanks to Daphnia tanks, planted tank filters, etc. and back again as with Biollante's setups...

 

Sorry for the delay in responding, been busy.

Doc7, the faucet I use has a problem being consistant. Hot and Cold are separate handles, and the hot seems to slowly diminish to a trickle as time goes by. So I may start out with water in the 70-75 degree range, but by the time I'm done filling, it's pretty much all cold water. Maybe I need a new faucet. Also, I can confirm I have not noticed any undue stress on my fish with the addition of cold water.

Dundadundun, I hadn't thought of a hose diverter... I'll look for one. Good idea. See, this is why I ask these seemingly obvious questions! And I'll check my LFS for those black filter pieces.

Jaafaman, I'm having a hard time picturing what you are describing, but I'm curious and would like understand this. Have any diagrams or photos you can share, or links to examples?

 

One each diagram of a self-levelling siphon:

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Ok, so looking at that, I understand this to be a drain loop (water flowing FROM the aquarium goes through this). Wouldn't water flow out of the top of that shorter loop, through the hole? or is the drain tubing big enough to handle the flow?

 

Aye, you do have to plan accordingly.

I use one made from 1/2-inch PVC plumbing on sensitive things like my Apisto fry tanks. That way, instead of drawing a large percentage of the tank and creating an almost instantaneous dilution delta, I add fresh water at one end while drawing off the mixed water from the other and freshen the tank a bit more gradually. Once I have the flow set up and going, I can also pull a little bit more water out while vacuuming without disrupting the process or having to stop the fill while I'm emptying the vacuum waste bucket (I know - buckets. So I'm Old School).

I looked up my original inspiration to find I'd mislabeled the system setup as "open" range when it's actually called a "circulating" range system. As illustrated on page 40 of Feroze N. Ghadially's "Advanced Aquarist Guide", published by The Pet Library, Ltd, of the Netherlands in 1969, it looks like this:

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where the lifting force for the tube connecting tank F's flow to tank A is simply an air pump. An air lift can usually supply a 2-3 gph flow, and that's enough to keep the inter-tank exchange to a decent level.

Using all of the tanks for seperate species tanks allows for the same individual spawning/rearing areas while taking advantage of the combined and inherently much more stable total volume in circulation. When I had the space, I've run it this way with a few double racks to more easily maintain breeding conditions across groups of fish that spawn under the same conditions.

Things like the Daphnia tanks I mentioned are another way to set up the downflow tanks. Ghadially mentions using the nutrient-rich flow to feed a high light, algae seeded tank to maintain Daphnia colonies. Now while I've seen folks do this with waste water before, I don't know of anyone trying to reliably filter algae from the flow within a loop like this. But I have seen some who run a Duckweed tank followed by a Hornwort tank to soak extra nutrients out of the water in the loop. And I've even seen one where the last stage was a trough instead of a tank, where the gravel-filled trough was used to grow emersed plants to serve as sort of mini-wetlands...

 

Thanks, Jaafaman. I know we have strayed off topic a bit, but I find this all very interesting and educational. I might have to experiment with something like this, either with a water change application, or even a sump filter overflow application. Although, I would probably still want some sort of overflow box to obtain a larger skimming area. I'll definitely read up on it some more.

 

That's easy enough. Just consider the exchange as having discussed both a method of accomplishing the large water change in question (the siphon) as well as an alternative possibility (although you could still work in large changes to the range system as well)...