Sick Danio & Algae Growth

[Alexis22]

I have a 5 gallon tank with a few danios and platys and one oto catfish. It’s been cycled for a few months. One of my danios this week suddenly started acting similarly to some I lost back when cycling my tank. I have been checking my water and besides having some but a safe amount of nitrates everything was normal. The only thing I noticed this week was the other danio was being overly aggressive and suddenly scaring him off from eating and chasing him into the corners. They were always pals so not sure what happened. But this danio has lost weight and his body and tail looks “S” shaped now. He can barely swim and sinks. I’m pretty sure I will lose him tonight.
If my water is ok what else can bring this about? Stress from the other’s behavior? It just seems so out of the blue. Everyone was great just last week! 
 

Also what can I do for algae growth? It’s growing on my artificial plants and sinking into my ornaments. The white filter floss was orange the other day when I cleaned the tank.  My catfish isn’t seeming to really control it at all. Suggestions? 

[nabokovfan87]

On 4/22/2023 at 8:18 PM, Alexis22 said:

If my water is ok what else can bring this about?

Can you post water test results?

On 4/22/2023 at 8:18 PM, Alexis22 said:

Also what can I do for algae growth? I

Any photos would be helpful. Different solution for different algae types.

[Alexis22]

Water test from today. 

[nabokovfan87]

I cannot speak to it, but I do believe I have read about PH causing bent spines.  I would have to deep dive into research on that, but potentially someone else can chime in that has more experience on the topic of bent spines.  Other reasons are commonly missing certain nutrients in their diet.

The water test generally looks ok.   In terms of fighting algae, lowering the nitrates would be beneficial.  You don't have a ton of plant load in the tank, so keeping them below 10 should be very sufficient.  When you do your water changes you can test immediately after for nitrates and that would give you a baseline.  After a few weeks of testing you'll have a trend for how much your tank is producing in nitrates between maintenance.  If you see them climb too high, then you'd want to increase volume or/and rate of your changes. 

The algae you're seeing looks to be diatoms.  This could be brown, green, or black (really is a red type) of algae that has started forming.  Each one has it's own reasons.  Good maintenance takes care of the first 2 and increasing the plant load/growth rate helps with BBA type of algae.  We will have to wait and see, unfortunately, how things develop.  Keep monitoring things and in the meantime we can look into the spine issues.