I jz introduced in a group of guppies and cordies into my somewhat established tank. But the guppies are dying one after another. The only sign they show is slowing down in movements and swim bladder malfunction reaction like losing control over its equilibrium with tail straight down. Die a few hours after the symptom emerges.

So far there are no cordies suffering such problem, but there are a couple cordies that show minor sign of trying to regain control over their losing equilibrium too. But their tails tend to float rather than sink like the guppies.

anyone experienced b4 pls teach d best & effective way to prevent this kind of sickness.. and how to cure the sick ones coz I have one in quarantine still.

This is pH/kH shock, I think the original water condition (pH & kH) where your newly bought guppies came from is higher/lower than your established tank. You have to quarantine those newly introduce fish before deliver them to your tank, the best way is to measure the pH & kH and adjust to suit the fish. This symptom not easy to cure, preventive is all.

oh thx regng2001..

oh regng2001.. u know d ph & kh for guppies & cordies??

Cordies I've no idea, Guppy pH is within 7.0 ~ 8.0, Hardness is 15 ~ 40dGH.

I think he asked you to check the pH/kH of the water both in your tank and in the shop from which you bought them and adjust your tank's pH/kH accordingly. Some of these breeders/sellers conditioned the guppies to their water quality rather than adjusting to known parameters for each type of fishes to lower the maintenance. Imagine if you have contrasting requirements, then you have to have separate filtration systems etc for each type of fishes. Since your information is lacking we cannot help you very much though e.g. established tank of what?? plants, other fishes, ornamentals.... etc.