It might be a chemical precipitate rather than a bacterial bloom. Perhaps at that time your DIY CO2 is running low, causing the pH to get high, causing either calcium phosphate or iron phosphate precipitate. Check your pH next time this happens.
MOne of my favourite aquarium was a 45 high with dd veiled angels, clown loaches, and upside down catfish. I had big swords with leaves going to the top. Looking at yours makes me so jealous. When the angels was small(i got them at 1/2 inch) I had them with large neon tetras in a twenty nine. They looked nice together but I knew their days together was numbered.
M
&' tall fin to fin.
QUOTE]
Sorry, my fingers aren't awake yet.
I meant 7" tall, not &".
Charles