just discoverd some minute little insects on the glass just above the water line.
the fish don't seem interested in them when i knock them off with my cleaning magnet,they just float back to the glass they are spider like in appearence but extremly small.
what on earth are they :-?

:-?

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i don't have any plants,and i never use the water from my purchases either,i catch them whist their still IN the bag!!!
HELP