Too long for a comment but not really a proper answer, so some advice.
I’ve heard of "ammonia spikes" which seems to tally with your story. I’ve had them myself: beautiful fantail, white tail, red lines appeared one morning but all readings were in the safe limits. No other fish affected. The blood streaks didn’t really disappear, either, although ...
Setup a fan pointing across the tank as a form of evaporative cooling. I assume though that would cool the top layer of water more than the bottom and I wasn't sure if the differential in temperature may make things even worse?
A fan is a fantastic method for lowering a tank temperature efficiently; when researching methods to effectively cool a 60 gallon ...
I have observed something different in my tank. She behaved fine when I only had java fern in the tank. But then I replaced it with large amazon sword plants, now she’s having a party on my plants!
I feed her quite well, but the sword plants are becoming expensive food for her now.
It is fecal material and decomposing plant material. That is why replacement filter elements are available. I use polyester fiberfill padding sold to make quilts; I cut it in rectangles to fit my filters and replace it as needed. I also use the garden hose to flush permanent type filters. The mud material also collects in certain locations in my pond; I ...
Fish in the pictures attached to your question looks like Gyrinocheilus aymonieri (Chinese algae eater, CAE for short).
Chinese algae eater (Gyrinocheilus aymonieri)
Image source: Wikipedia.
Image source: aqualog.de.
Image source: aquascape.ae.
Chinese algae eaters are fish from the carp family Gyrinocheilidae (they are the only one genus in it); they are ...
I assume you mean the weird color of the torso of the guppy.
It looks so weird because it's actually transparent and you can see the organs and the spine inside the body. Here's an example of 2 completely healthy guppies:
image source: Phys.org
The lower fish is completely transparent. You can see the spine and the silver and brown things in the stomach are ...