hoppycalif

Two questions people, including me, always ask are: How do you know the ppm of CO2 will be the same in the drop checker bubble and the tank water? And, how long does it take for the ppm of CO2 in the drop checker to match that in the tank water? I did some testing today to see if I could answer those questions.

I took a 2 cup measuring cup, mixed distilled water and baking soda to get about a 2dKH batch of water. Then I loaded the drop checker bubble with that water - it took 2 ml to do so. I added 4 drops of pH test reagent to the bubble. Then I installed the drop checker in the 2 cup measuring cup, with it just below the water surface. I took a length of air hose and used it to blow bubbles into the water to build up the ppm of CO2 in the measuring cup. About a minute of blowing got it to a pH of 6.5. I kept checking the pH until it rose to 6.6, which took about 30 minutes, then blew more bubbles for a minute and repeated that every 30 minutes. At various times I recorded what the pH of the drop checker water was, using the pH color chart. And, I charted the results:



You can see that the ppm of CO2 in the drop checker does equal that in the tank water, as closely as you can read the color of the test kit. And, it takes about 3 hours to reach equilibrium with the tank water. I wish it were faster in response, but 3 hours is certainly usable.

graedog

Just a quick thank you

I found this post really interesting and helpful

Graeme

swifty1

Great post! - I've ordered 2 drop checkers, one amano style, one pear shaped, but one question - should the KH in the bubble be the same as the KH of the tank water?

or should it be worked out to give a green colour with the ppm level I'm seeking?

I think its the latter?

hoppycalif

The KH of the water in the bubble can be whatever you want to set it at. If you pick a KH of 4dKH, the bubble is green at 30 ppm of CO2. If you pick 5 dKH, the bubble is green at about 40 ppm of CO2. And, green is the most unambiguous color you can look for in the bubble, so it is best to chose the KH that goes with green at the ppm of CO2 you want to maintain. I am using 5 dKH for mine, and I'm having no problems with the fish at all. I am very tempted to try 6 dKH in the bubble, to get 45 ppm of CO2, but I haven't done so yet.

Another reason to use the KH that corresponds to green at the ppm of CO2 you want is that you then can detect ppm's that are much higher (yellow) or much lower (blue). If you used a KH where the color was yellow at the desired ppm of CO2 you couldn't tell the difference if the ppm were much higher. By that I mean, it is best to have the desired ppm give a color that is in the middle of the scale, not at one end of the scale.

swifty1

That's nice and clear Hoppy - thanks!

Just waiting for my drop-checkers now!

hoppycalif

Another way to make a DIY drop checker is to use a small clear plastic bottle. Cut off the open end of the bottle, turn it over and glue it back in place upside down, so the neck extends into the rest of the bottle. Then attach a suction cup. Does anyone know what to use to glue P.E.T. plastic? It is a form of polyethylene so no glue I have found will stick well to it. I made a prototype this way using a bottled water bottle, but the joint didn't hold up at all. It works nicely though, but those bottles are really too big. I bought a 2.5 oz bottle of aloe and tried to use it but I heated it too much with hot water to clean it and the bottle suddenly shrank to a twisted mess! If that had worked it would be a $2 cost to make one.

dennis

You're best bet for sealing that is to use heat and fuse the two parts together. Make sure the two peices are equal by careful trimming and/or sanding with the two halves jammed together. Then, heat a piece of metal on the stove or with a torch until you can just barely melt the plastic with it. I don't think there is any glue that wil stick to it for more than a few days.

hoppycalif

Thank you Dennis. I will try that next. My grocery store had some little 2.5 ounce bottles of a hand cleaner too, but the bin was empty. That should work better than the aloe bottle, and it's $2 too. Hey, big spender!!

hoppycalif

I dug down deep and bought another 2.5 oz bottle of aloe to try to make a drop checker. These pictures show my progress:

First, the bottle still filled with goo, with the razor cut across the top:


After making another cut to get rid of the excess height:


After using sissors to trim the pieces:


The pieces ready to assemble:


After "welding" the bottle parts together, and attaching the suction cup, plus adding a bead of silicone to make it leak tight: (as it sits here, it is upside down - the opening will be on the bottom in the water.)


Welding isn't easy. I used a knife blade heated with a torch, using the scrap part of the bottle to judge when it was hot enough. Then I gently rubbed the joint with the hot blade to melt it together. Unfortunately, that left a couple of slight gaps which could not be sealed by any further welding. So, I used some aquarium silicone sealant to seal the entire joint.

The suction cup is installed in a hole that is melted into the side using a drill bit heated by the torch. I started small and kept going larger until the suction cup could be forced into the hole. That is a bit tricky too.

Now, you, along with me, are going to have to wait for the silicone to dry to see if this will work. (My faithful assistant, Igor, is circulating now accepting bets!)

dennis

The weak part to this may be the hole for the suction cup. Hopefully though, the rubber will swell slightly when wet and prevent any leakage. The silicone may not stick very well but if it is only for small holes it will probably be OK. In hindsight, a way or heat crimping the joint may be best, similar to the way they seal those damn packages for portable electronics. Heated pliers may do the trick.....