Adequate lighting for chaeto?

[Theulli]

This may be unanswerable but I have a chaetomax (9W, I happened to have it on hand so that’s what I am using!) suspended about five inches over my chaeto, which is about three or four inches under the water. This is in a 100g setup with a 29 gallon tank I have modified into a sump.

My phosphates and nitrates are not zero but in the desirable/well tolerable ranges. I am not using the chaeto as much for nutrient export as for pH balance at night and a pod habitat . I just started this as an experiment because I found my pH unacceptably low in the mornings, and it appears to be going pretty well for those purposes, though I can’t rule out that the better pH balance is simply my simultaneously bumping my water changes up to 10% every two weeks instead of every 3-4

However I don’t want to nutrient bomb my tank by underdoing it and having the stuff melt. 9W seem ok in this setup or should I bump it up?

Thanks!

 

[ZombieEngineer]

I have a 65g with 29g sump and used a 20W with a 16 hour photoperiod.

It was too efficient and I let my Nitrates tank to 0.0 and got dinos. Dialed it back to 10W at a 12 hour photoperiod and things seem pretty stable.

9W should be fine for a while and if it doesn't keep up, you can always upgrade your light later. Either that or get a dimmable one, start at 9W and work up.