I read this topic with great interest and feel that I ought to add my 2 pence worth. Firstly being an innovative type, a method to check the pH of the water in a bag without opening the bag would be quite easy using a hypodermic syringe. Firstly place the required drops of the chemical dye in the hypodermic, then pierce the bag with the Hypodermic needle below the water line and draw out the required amount of water and read against the colour chart. Easy. No atmospheric contamination at all.
Now whether there is a pH climb or crash when a fish bag is opened I would imagine that it would not happen in an instant and therefore should easily be counteracted and if you want to be exact in your preparation, once you have established the pH in the bag (above), water can be pre-prepared before the bag is opened. However I think that all that is totally unnecessary.
Lets give you a little insight into the annual conditions that many of our Corys have to go through. After the rainy season water levels recede and especially with the flood-planes and lake species, as it recedes the water becomes more and more acidic, so much so that thousands of fish actually die as the dry season comes to an end. When the rains come again the pH rises very quickly and the usual result from this is spawning activity. A sudden drop in pH is far more dangerous than a sudden rise, however if a drop is counteracted with new clean higher pH water there should not be too many problems. In fact this is one method I use to induce spawning with a few species.
Miss Wiggle,
Sorry to hear of your losses. C. hastatus are not the easiest of Cory species to acclimatise and I have found the slower it is done the better. I actually do not agree with the Bryan method. I actually open the bag and check the pH and conductivity to see how different they are to what the fish are going to be putt in. My normal procedure is to release the fish with the water they came in into a largish container, which is usually the polystyrene box I transported them in. I then syphon water from the tank they are going to be placed in using a piece of air-line tubing. The change over is quite slow and does not subject the fish to any sudden changes either in pH or hardness.
One of the biggest dangers with shipping Corys is when traders fill the bags with pure oxygen, not good news. Corys take in a bubble of atmospheric air at the surface and pass it down into the gut where there is also a fair amount of bacteria, this air bubble acts as a swim bladder, but they absorb the oxygen from it and when the oxygen has been absorbed they nip up to the surface for another gulp. Now if pure oxygen is used in the bag this can have the disastrous effect of feeding the bacteria, which multiply at an alarming rate. This is in my opinion one of the causes of the so called 'Red Blotch' disease.
Shock/stress is probably the biggest cause of Cory deaths, or any fish for that matter, reducing the causes of stress as much as possible will help to settle new Corys.
Ian
