Over Skimming

[Oopkrane]

I have a 130l total volume system and until recently been running a cheap and nasty skimmer. Been dosing NO3PO4 all along. Switched over to a Reeftek TS1 (running 24/7) and now my macro algea in sump is starting to die off and getting cyano algea on substratein DT.
Could this be due to over skimming?

 

[Visser]

Yip, very possible.
Do you take readings for nitrates & phosphates in your tank? If not, you might want to consider it.

When using no3po4x with a underrated skimmer... Not all the nitrates & phosphates gets removed. The algae gets acclimated to the higher nutrients in the tank, & grows on that.

Now, once you upgrade your skimmer, the nutrients (no3, po4 & other dissolved organics) gets removed a lot more effectively (with the help of no3po4x).Now, you suddenly get a fall in drop in available nutrients, & the algae starts to starve...
A quick summary of what's happening...

 

[Oopkrane]

Thanks, but why is the cyano suddenly growing?

 

[Visser]

Could be due to an imbalance in redfield ratio (more phospates than nitrates within ratio)
Have you measured no3 / po4 ?
Could also be due to the sudden increase in decomposing material caused by the dying algae...
Remember, algae absorbs nutrients. When the die, there will be a sudden increase in nutrients again, & cyano just loves decomposing material!!!