Hi,

I've been producing large amounts of Gracilaria fertilizing with about equal amounts of NH4NO3 and (NH4)3PO4 once a week. I help produce the Gracilaria for feed for abalone and have been seeing some epiphytic growth of green filamentous algae. Is this a good ratio or should I reduce the amount of phosphate because I've heard the red algae don't require as much/or any of it? What about KNO3? Would the Gracilaria get better growth, less fouling from green algae with KNO3? I'd appreciate any guidance here. Thanks!

Christine

Reduce the PO4 to a 3 to 1 ratio, and you may be able to work it down from there. While red algae don't require as much I don't believe it can be eliminated all together for Gracilaria. I wish I could be more specific, but it's been quite awhile since I've done any tinkering with macro algaes, and they were never really my field. Cultivation has come a long way since then. HTH. Prof M

I'd suggest less PO4.
No NH4, use KNO3 or Ca(NO3)2 instead.

All marine macro algae do well with higher NO3 than you can stand than with NH4.

You can still add a trace amount of NH4, but a few small damsels etc will do the same job and be better at all.

Iron is a big one.

I'll have the marine trace iron out here in 3-4 weeks.
For now, use DTPH based iron, Tropica is ideal and far better than other marine Kent and other junk they sell.

Regards,
Tom Barr

Thanks Prof M and Tom for your replies. I will try reducing the PO4 next time. So, should I just keep the NO3 amounts the same from what I had been using, but with the KNO3 instead? The problem is is that I have very large tanks that I am dealing wtih (about 3600 gal), so using products like Kent are not practical. I am not familiar with DTPH or Tropica, but will look into them. We normally use regular agricultural fertilizers since we generally use 200-300g per dosing, per tank.

Thanks for your advice,

Christine