Reduce photoperiod all at once, or slowly? Also, cyano question.

[Tired]

Have recently gone from "oh, some new algae" to "that's a surprising amount of growth" to "better check my photoperi- whoops". 

Long story short, the light over my tank is plugged into a light timer. The same timer I'm using for some terrarium lights, where I'm growing plants. It's way too long of a photoperiod, something like 15 hours, I think. I'd like to cut it down to about 8. 

Should I do that all at once, or gradually? I don't want it to throw a fit and die off. It's kind of an assortment of algaes, including a decent bit of hair algae, and a dash of cyano into the bargain. 

Test kit's in the mail, but nitrates and phosphates are within the happy zone for zoas- mine are open. 

 

Unrelated: how would I grow cyano on purpose, in a fishbowl? I think it looks sort of neat. That, and it first evolved over 2 billion years ago and is responsible for the oxygen in our atmosphere today, which is fascinating as all hell. Just keep it in there with light, water changes of (used) tank water, no flow, and no competition? I'm kind of curious what sorts of shapes it'll grow into if I pipette some out of my tank and let it run absolutely wild in half a gallon of water.

[mcarroll]

That change in photoperiod should be fine to do all at once.

 

Let us know what you get for test results! 👍

[Tired]

Test results wound up being 0 of everything in the nitrate cycle. Time to start feeding the tank a bit more, I reckon. Between the algae and some macroalgae it was absorbing all my nitrates, which is pretty cool. I'm trying for a tank that will be able to keep its own nitrates low, so that water changes will be mineral replenishment only. 

My cleanup crew took out basically all the hair algae pretty fast. I have a spot of cyano in one area still left, and still a bit of hair algae here and there, but it's at totally reasonable new tank levels instead of "whoops".

 

Also, my half-gallon bowl with cyano in it is also full of breeding copepods. Not really the intent, but I'll take it!