Suspected velvet!

I’m new to fishkeeping, and I was wondering if someone could advise me on these yellow patches that have appeared on my female guppies.

They’re quite small, and are located near the front fins. After doing a bit of research, I’m really worried that I’ve got velvet in my tank, although apart from these patches appearing the fish are behaving completely normally. I can’t see any patches on any of the other fish in the tank too. I’ve bought a medication for velvet, though I just wanted to get some advice or even some confirmation of what this might be before I go ahead with treatment.

Thank you!

Can we have some pictures?

Sorry if the pictures aren’t too clear, but it’s that small yellow/orangey patch near the front of her body. It’s very hard to tell if my other guppy has it, as she’s completely yellow anyway.

Hi and welcome to the forum

You should always identify the problem before adding chemicals to the tank because chemicals harm fish as well as disease organisms, and if you don't use the correct treatment for the disease, you are wasting money and poisoning the fish for no reason.

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Is the fish rubbing on anything in the tank?
Velvet causes fish to rub on objects in the tank. As the disease spreads, fish get covered in a gold yellow substance. An easy way to check for velvet is to shine a torch on the fish after the tank lights have gone out. If there is a yellow/ gold sheen on the fish, and the yellow/ gold is not part of its normal colouration, then they have velvet. You can use a camera with flash to photograph fish after dark and it will also show up velvet if they have it.

The safest treatment for velvet is heat. Raise the water temperature to 30C (86F) and keep it there for 2-4 weeks. Increase aeration/ surface turbulence when using heat or chemicals because they reduce the oxygen level in the water.

Before treating the tank with anything, wipe the inside of the glass down and do a 75-80% water change and gravel clean the substrate. Make sure any new water is free of chlorine/ chloramine before it's added to the tank. Clean the filter too if it hasn't been done in the last 2 weeks.

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The following link has information about what to do if your fish get sick. It's long and boring but worth a read when you have some spare time.