hoppycalif

One flat piece of acrylic has a hole in it. The membrane goes across the hole, over the O-ring, and then between the two pieces of acrylic. That leaves a disc consisting of membrane, piece of sponge soaked with KH reference water, acrylic, with the O-ring sealing in the KH reference water. I wasn't too happy with this design, and I'm not all that sure the tyvek membrane doesn't leak a bit. Personally, I am giving up the quest for faster response, preferring the simplicity of not using the membrane.

Jubs

Thank you Hoppy I understand exactly what you are saying now. I might try something like this soon thanks for the great write up and trying different types!

Color Me Blue

Can I say WOW! This has been a very informative thread. This answered my drop checker questions. Thank you for taking the time and energy to share all this.

dirtmonkey

Hoppy Wrote:
> I'm not all that sure the tyvek membrane doesn't leak a bit

Tyvek is only a one way street when a liquid with surface tension (like water with no surfacants) is only on one side, and air on the other. It is ALWAYS permeable to water vapor. Only surface tension of the water resisting against the small pores in the polyester allows it to hold water- but not permanently. It is a two-way street for water and even much larger molecules when wet through. Its pore size is not regular, there are larger and smaller holes. I know from experience with sterile cultures that it can only be effective in keeping out viruses and even some bacteria when it is dry on both sides. Those are obviously much larger than organic acid molecules of all kinds. It worked for you temporarily, but I think the true semipermeable membranes with the right structure for the job would be the only long-term solution (pun intended).

But I agree with you now that the hassle doesn't sem to be worth the gain over the regular partial pressure gas exchange testers the thread started with... now off to make one for myself (yeah, when I get around to it... )

Zamboniman

Whipped this DIY Drop Checker together in about 5 minutes with stuff I already had. Doesn't look too bad in the aquarium, now we'll see how it works. I just put it in so the regent is still blue. It's the air type rather than the membrane type so it'll take a couple of hours.

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Squawkbert

Nice job on the "3-jigger drop checker"

hoppycalif

Wow! What a neat and easy way to make one of these gadgets. The only suggestion I have is to keep the quantity of water in it to a minimum to speed up the reaction time.

Blacksunshine

lol. nice shotglass DC.

If anyones interested, I will be making some # of DC's in the next week. If you wanna save yourself some time and hassle PM me.

Laith

Not bad! What a simple but effective idea.

I assume that's silicone you used to put it all together?

Squawkbert

Hoppy - I suspect it (speed) may also be a function of surface area than of volume in the "air gap" checkers. I've got one (air-gap one) that holds <2mL of indicator solution but it's in a tall, thin shell vial. It reacts slower than the membrane one (inverted bottle w/ hole in cap) in the same tank.

Once, it went yellow so I pulled it and stuck it to the outside of my tank, it took 3 days to change back to green. My membrane one went from blue to green in 3-4 hours when I added it to my 5g tank.

I need to refill the one in my 46g tank as the 96W light has not been kind to the indicator dye. I think I'll mount it a lot lower in the tank when I refill it (maybe in some shade provided by the sword that's taking over).