1. The air routinely brings in bacteria, fungi, cyano depending on location, and micro algae that we see in aquatic or marine setups. Easy confirm: take a cup of water and dose it with planted tank fertilizer, set it in your windowsill and keep it topped off. Give it a few months (winter=cold=slower) doing nothing but topped off, colors change / scums form and the above manifests in varying ratios.
A new reef cycled that has no animals at all, just rocks formerly dry and dry sand will mimic in its invasions much of what the windowsill cup reflects, but the reef is ready to express new invasions like diatoms and reef associated invaders the very instant we add a snail. Or a pod. Or a tiny chunk of lr from another tank— a vector for the more reef tank specific items. no windowsill cup can ever get invasive dinos for example, or valonia- direct cellular transfer required. Dry sand use is rare, the majority of sand using cyclers are on wet bagged stuff, that counts as instant vectoring. Diatoms are universally associated with reef substrates and fluid/ wet bagged sand is an often not considered source since it looks clean in the bag.
2. Subjective answer and no five posters will agree. It’s my opinion that cycling is for bacteria you can’t see but you can still measure, and purposefully seeding your tank at any time with invaders like cyano and green hair algae have nothing to do with nitrification. We get those invaders in nine year old tanks, invasions have nothing to do with cycling but in 1982 they were sure it did and nobody updated the manual. All tanks will develop uglies if they’re left unguided at the start; I merely advocate cleaning them out like a gardener tends for dandelions. Everyone else leaves them in, and hopes for a near takeover as a -good sign-
The fact so many cyclers think these two are requisite actions is why I have ten years of algae restoration threads handy, running to this day with new entrants, keep the practice going by all means we love the work and challenge of undoing purposeful invasions.
3. Coralline needs light but not much and too much early light causes algae, seek your balance. Coralline is a handy bio indicator agreed, but if it doesn’t grow for someone there are other timing methods that can be used to cycle a tank besides coralline.
https://www.reef2reef.com/threads/the-microbiology-of-reef-tank-cycling.214618/
That link shows why I like BRS work. We never collaborate on anything yet we use highly similar approaches on actions like cycling, sandbed maintenance etc.
the type of procedural advice that can be offered in large work threads or on production videos such that consistency in outcome can be measured across a thousand web poster attempts isn’t widely varying advice...it’s got some overlapping themes for sure.
we will do our best to keep learning and sharing!
