The think the Eheim diffuser works very well. I saw it for $15.99 at Drs. Foster & Smith. I bet all diffusers use the same glass sintered disk. My pH is normally about 7.8 and I get it down to 6.7 in my 75 gallon tank at a kH of 6. In the 125 gallon tank it is not quite enough, but two Eheims would be perfect. I have built several reactors and they where all inferior to the little Eheim. The last reactor I built is three feet long and 3 inch diameter. I am using it on the 125 gallon right now and it is slightly better tha one Eheim diffuser, but a three foot reactor is pretty hard to hide. I would much rather go with two Eheim diffusers.
The Eheim diffuser comes with a high pressure check valve. I think it must be pressured to about 15 psi for it even to open up. It has a metal spring in it, and overall I had a lot of trouble with the diffuser until I threw the check valve in the garbage. I replaced it with a cheap Tetra check valve from Petsmart, and I put a $12 Clippard needle valve in the line for regulation. I think this is the secret to using the Eheim diffuser.
In fact for you reactor affectionados, I will buy your used Eheim diffuser if you think your reactor is better.
Steve, how often do you need to clean the Eheim diffuser. I have one in storage that I gave up for a Plant Guild "in the tank" reactor. It works well in my 75 but it is another piece of hardware that is visible and now I want a cleaner view. I suppose I could pop the Eheim back on and see how it works. Used to not have a glass cover - now am using one.
It looks like they could clog up with slime, but mine seem to clog up on the top surface with algae. I have algae problems in both my 75 and 125 and until this week the back of the tanks were getting a lot of light from the windows. I just painted the back glass of the tanks to eliminate this light. The algae builds up in about three weeks. The diffuser still works but I notice that the bubbles are larger so I clean the disk then. I think the CO2 encourages algae to form on the disk.
I clean the disk with a 50% bleach solution in a small drinking glass. Its clean in about 20 minutes.
The one thing I like about the Eheim diffuser is that it is small. I compare it to my big reactor which you can see at: http://users.ev1.net/~spituch/Steve's Page/Aquarium/hardware/DIY CO2/DIYco2.html
Talk about a pain-in-the-*ss, this thing is a bear to dissconect to take outside to clean. The view ports at the top and bottom which I use to see the bubbles scum up with brown algae slime and then I can't count the bubbles.
l would rather clean the eheims every few weeks when I wipe the glass clean, than struggle with the bear every couple of months.
Besides, based on the much larger surface area of the smaller bubbles I still disagree with most of the aquarium community and still feel that the diffuser is more efficient than a reactor.
Thanks for the info steve. Wow your co2 reactor is a monster. DO you have a picture of the eheim diffuser? I searched drfosterandsmiths and couldn't find a closeup pic of the diffuser. Would like to check it out. Did you place the diffuser directly infront of a filter/powerhead for the current to disturb and take the co2?
I don't think it matters where you put a diffuser. Of course the lower it is the longer it will take for the few bubbles left to reach the surface. Even if some of the bubbles reach the surface, if you discount those bubbles, I've stilll estimated that there was more surface area of the dissolved bubbles than the one big bubble going into a reactor. The best thing would be to put a diffuser beneath a reactor but I don't think that is necessary.
The top right picture at the previously referred page at: http://users.ev1.net/~spituch/Steve's Page/Aquarium/hardware/DIY CO2/DIYco2.html
shows my eheim diffuser in the bottom right corner of the tank. The co2 is fed at the bottom of a clear bubble counter chamber and the sintered glass disk is in the gray plastic top. It is also shown in the picture at the second row from the bottom of the page when I was trying to feed a smaller reactor with the fine eheim bubbles in order to increase the efficiency of the reactor. The bottom bubble chamber is blocked by the black suction cup. As it turns out the eheim worked better just by itself.
Yes, plantbrain did design some alternative ways to diffuse CO2 into the water. The two basic ideas were to fill the water with microbubbles of CO2, because plants can take up gaseous CO2 easier than CO2 dissolved in water, and a way to recirculate water with CO2 in it to get 100% of it dissolved into the water.
Another way is to get one of these:
I got my last one from Amazon.
Poke the CO2 hose into the bottom filter compartment, preferably with a small diffuser, like a piece of bamboo, on it to generate smaller bubbles, and let the filter pump break up the bubbles into microbubbles and spray them around the tank. This is the method I use, with yeast/sugar DIY CO2, and with a small checkvalve on the end of the CO2 hose. With this I get 20+ ppm of CO2 in a 65 gallon tank, with two 2L bottles. It has been my favorite way to use CO2.