Dead Fish Society

I'm no icthyologist, but I do have an interest in keeping fish. I have three tanks, a 50l, a 100l, and the new addition, a 225l. I recently stocked the 225l with 10 Cardinal Tetras, 5 Penguin Tetras, 4 Clown Loaches and a red spotted Plecostamus. Unfortunately the 4 Clown Loaches have expired along with 5 of the Cardinal Tetras, and one of the Penguin Tetras. I have done regular water changes, and 'cycled' the tank, but to no avail. It appears that the dead fish caught the dreaded white spot disease, and despite using the appropriate chemicals, I couldn't save the fish. Now I'm getting a little gun-shy, and I'm less than enthusiastic about wasting more money on fish corpses ! The remaining fish appear to be healthy.. but who knows how long that will last.