Another simple pH Drop Checker

[Wasserpest]

Okay... listen up kids! In todays science class I'll show you how to make a pH indicator for your fishy tank.

We will need the following:



- an empty small plastic bottle, like they give you in hotels to wash hair and stuff
- a small rubber band, like they use when you buy fish in the pet store
- a rubber suction cup from the spare bin
- a zip tie
- a breather bag
- something made out of white plastic, like an old credit card, Nutella cover, etc



To assemble, poke two holes into the suction cup and push the zip tie through it. Cut the plastic bottle with a sharp knife, maybe in half. Cut a piece of white plastic that goes on the bottom of the container, which makes it easier to see the coloration of our pH indicator solution. Cut a piece of breather bag to fit over the opening of the container.



Twist tie the suction cup to the container. Drop the white plastic piece into the container, and test the rubber band to make sure you didn't cut the breather bag too small. Add some 4 dkH water and indicator to indicate 30 ppm, or use 3 dkH for 22 ppm, 5 dkH for etc etc.



Works. In this case, the air space is a bit too large, so the drop checker tilts upwards. Either I need to cut the container shorter, or add more water.

After looking at it for a few weeks I get tired and throw the thing in my "interesting but useless gadgets" bin.

[jinx©]

Pretty resourceful...Maybe try an empty tictac container?

[gmccreedy]

To keep it from leaning forward, how about centering the container with the zip tie. Should balance it out.

Nice little toy there.

[Wasserpest]

It's just too much of an air volume in there... no problem, just realized that after I took the picture.

Using a rectangular container seemed like a good idea... looking through more solution makes the color easier to see. However, zipping it with a zip tie makes it bow a little bit, which in turn makes it more difficult for the rubberband to contain the plastic cover sheet.

I used a short piece of plastic straw to keep the sides from bowing in... that works well.

I wonder if using a white opaque container instead of a clear one would make for a better visible indicator... <off to more tinkering>

[crazy loaches]

Nice.

[KevinC]

Maybe a silly question: Why not invert the setup? Then there would be direct exchange across the breather bag into the test solution - no air gap. The bag does not allow water to cross, so I assume it also does not allow ions (kH) to cross either.

Kevin

[swylie]

Try inverting the container so there's no air gap, just dead air above the drop checker fluid. There's no need for an air gap if you have a waterproof gas permeable membrane.

Edit: I'm too slow. ^^^

[tazcrash69]

I had tried something similar using a 5 ml API test tube (inverted with ~2ml of liquid against membrane), and the solution ended up looking like a tequila sunrise with yellow at the bottom, and fading to green on top.
Although I attribute this to the narrowness of the test tube vs the depth of the fluid.

[Wasserpest]

Originally Posted by KevinC

Maybe a silly question: Why not invert the setup? Then there would be direct exchange across the breather bag into the test solution - no air gap. The bag does not allow water to cross, so I assume it also does not allow ions (kH) to cross either.

Kevin

Originally Posted by swylie

Try inverting the container so there's no air gap, just dead air above the drop checker fluid. There's no need for an air gap if you have a waterproof gas permeable membrane.

Not a silly question at all. The reason why I didn't want to invert the contraption is the cheesy rubber band. Pretty sure the solution would leak out/water would leak in. With right side up, air trapped under the rubber band prevents any fluid exchange.

I'll try that though, maybe with a better rubber band, and the white/opaque bottle. I'll post pictures if it works!

[frozenbarb]

o.O i tried a o ring and it leaked no matter how much i tied it.

Check for leaks how long has it been up?

[swylie]

See if you like this setup to prevent leaks around the rubber band. BTW, anyone know if it's possible to buy kordon bags locally at retail? I have a feeling it would work better than tyvek. Tyvek that's designed for being printed on is corona discharge treated and only water-tight to 15" of head.

[Wasserpest]

Swylie - Your screw cap design might be better sealing than the rubber band. I just picked the easiest thing I had laying around.

Frozen - No leaks at all, if done right site up like in the photos. I haven't tried upside down, that might cause some leaking issues. O-ring is a good idea too, not sure if they stretch over time and then don't seal anymore.