Your camera doesn't like yellow objects
. Most digital cameras have trouble photographing yellow, white or black objects and they tend to focus on other things and not necessarily what you want. I can't tell if the electric yellow has Ich from that pic
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If fish are dying after you treat you are possibly overdosing the tank.
To work out the volume of water in the tank:
measure length x width x height in cm.
divide by 1000.
= volume in litre.
When you measure the height of the tank, measure from the top of the gravel to the top of the water level.
If you have lots of rock or driftwood in the tank, remove them when you measure the height because they displace the water.
You can use the Calculator/ converter under the "How To Tips" at the top of this page to convert litres to US or British gallons if you need to.
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Before you treat any fish tank, wipe the inside glass down, do a 75% water change and complete gravel clean before adding any medication. And if you have a power filter, clean that too. Wash the filter materials in a bucket of tank water then do it again in another bucket of tank water, then put the materials back in the filter.