Bubble counter lets you check exactly how much (in bubbles per minute) CO2 you are adding. A diffuser is the bit that helps the CO2 get into the water column.
Also (not that you asked) but don't get confused between a bubble counter and a drop checker! Thats what I did when posting on a thread last week
A bubble counter is as NRY says above, for counting how much CO2 is being produced and how fast. With a name like "Drop Checker" it sort of implies the same function but its not.
A drop checker is a little glass bubble filled with a liquid that sits inside your aquarium. The liquid reacts to the amount of CO2 in the aquarium and changes colour accordingly, telling you if the levels are safe for your fish etc.
Not quite correct but close enough.
A bubble counter acts as a
guide as to how much CO2 is going down the line. Different systems will vary in how many bubbles they need to produce the same amount of CO2 due to the length of line, NRV, bubble counter etc all reducing flow etc.
Foe example when I use yeast based kits I will have approx 60-90 bubbles per minute to produce the same amount of CO2 as 4-6 bubbles per minute when I use pressurised. (I assume this is down to the difference between pure CO2 from a cannister and CO2 produced by yeast kits)
Different makes of NRV may work differently to each other therefore some letting through small amounts producing one bubble and others needing larger amounts and therefore needing more pressure to still produce one bubble. Of course the latter will result in wanting a lower bubble rate through the bubble counter.
With this in mind the bubble counter can be used as a guide only because 4bpm for my tank on pressurised will not necessarily mean that someone else with the same size tank will be OK with the same. This is why most CO2 users have a drop checker (also know as permanent CO2 test)
A diffusor is the final part of the CO2 system and dependant on which diffusor you use will undertake the task of diffusing the CO2 into the water wasting as little as possible.
For example if you just had the end of the line in the water. Your bubble would come out, go straight to the surface and you would lose almost all the CO2 you are producing as little would diffuse with the water.
If you were to use a ladder, this makes the bubble travel a longer distance before it can hit the surface and the bubble will noticably get smaller as it climbs the ladder which is the amount that is being diffused.
If you were to use a ceramic diffusor the idea is that it produces lots of very tiny micro bubbles (mist) rather than 1 big bubble and therefore they diffuse with the water much easier on their way to the surface.
A drop checker needs a solution in it that is 4dKH (and not the solution that is supplied + tank water that the instructions say) The 4dKH will have a relative Ph
When you fill the drop checker with 3-4 ml of the solution and add 3-4 drops of Ph indicator the vacuum in the drop checker will have air exchange with the solution and therefore the Ph indicator will turn the solution blue.
As time progresses in the tank the CO2 in the tank water will (as it does at the waters surface) exchange with the air in the vacuum in the drop checker and slowly but surely the Ph indicator in the drop checker will change the colour as the CO2 goes up.
The drop checker may be up to 2 hours behind the actual tank water's CO2 content as the exchange will not take place instantly but it will give a clear indication of how much CO2 you are getting permanently as you can look whenever you pass the tank and see if things are OK or not. Much better than having to do tests several times a day or even once a day.
In summary the bubble counter and drop checker are very useful guides with different uses:
The bubble counter lets you access a rough idea of how many bubbles YOUR system should produce to send the drop checker green.
The drop checker lets you see if you are roughly on the money by being green or if you are too low (blue) or dangerously high (yellow)
Andy
