Thanks for the info on those fish guys, they are all nice and have got me thinking.
Anyway, the venerable Royal Mail managed to fight their way through today`s blizzard to deliver the following from AE.
This picture is of my Boyu drop checker.
The purpose of this strange snail like piece of glass is to give me a good indication that my tank CO2 levels are running at 30ppm. It is done by adding a few drops of the liquid in the green capped CO2 test bottle to the bulb on the left of the dropper ( I actually use the drops from my Nutrafin pH test kit, but more of this later). Then you need to add a few drops of reference solution at a carbonate hardness of 4dKH, which is basically RO water with some BiCarb added until 4dKH is reached. The 4dKH reference solution is pure, without any unwanted influence on its pH, unlike using tank water, so adding the test drops to the solution we should see a dark blue colour (mine went beyond the upper colour scale of pH 7.6 on my Nutrafin chart).
When the dropper is fitted below the water level in the tank, an air gap is trapped between the tank water surface and the reference solution. What happens now is that the amount of CO2 in the tank water will, over the period of an hour or two, equalise with the CO2 in the dropper air gap, and thus affecting the reference solution. The colour of the reference solution should change from blue to green, with green corresponding to a pH of 6.6 on the Nutrafin chart. Correlating a carbonate hardness of 4dKH against a pH of 6.6 and we get a CO2 level of 30ppm. If the solution remains blue then CO2 levels are too low, and if it goes beyond green and turns yellow then CO2 levels are too high.
The next picture shows a Clearseal aquarium base mat from my LFS which the tank will sit on to ensure the whole of the base is supported when sat on the cabinet. The large silvery bag on the right is ADA Aqua Soil Powder, the Rolls Royce of substrates according to experienced aquatic gardeners. I am really looking foreward to seeing the results from using this stuff, because it will probably represent the biggest change between my current 120l and this new project.
So, why do I use the Nutrafin pH test drops as opposed to those that came with the CO2 dropper? Well, I am fortunate enough to work at a power station where millions is spent on water analysis. By comparing my Nutrafin kit against the lab results at work I can say that it is quite accurate, or rather, my interpretation of the test kit colours isn`t too far off the mark, so I prefer to stick with a known quantity.
I feel I should also mention the accuracy of the JBL KH test kit. My 4dKH is, in my opinion, a very accurate reference, having prepared this using very accurate measuring equipment and exceptionally high quality RO in the work`s lab. I added four drops of the test kit and the water was still blue, but by adding the slightest fraction of a drop more and the water turned yellow. So, I believe this test kit can be considered to be pretty accurate as well. Its just a shame I rarely need to use it.
I hope this wasn`t too boring a rant, but the full info on using a 4dKH reference can be found here, for anyone that is still awake. It has a nice picture of the drop checker in action, too:
http
/www.fishforums.net/index.php?showtopic=169942
Cheers, Dave.
Just joking, they look great in your tank. I was going to go rock hunting today, but Mother Nature decided otherwise.
They are good for something then, the wonder of kids 
Though in all fairness, I have dealt with it in the past. 
Keep the pics coming.
