help fish suddenly dying

hysterical

AC Members
May 20, 2009
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ive kept a few fishs in my 20L tank
got a few corys,swordtails,guppies and rummy nose.

they were fine ever since i placed the driftwood in.

ive boiled the wood for 3 days and place it in.

2days later my guppies died and now my swords.
my corys seem really ill.

need help~ i recently water change, but i think i did some nitrate spike by moving my gravel around.

is there anything i can do at this stage to prevent more death?
 
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