Hello,
There is a difference between keeping decorative macroalgae, and a planted saltwater tank. I have done both. I love macroalgae, it keep the tanks water pristine.
Now for the planted tank story:
To have a planted tank, I needed a deep sand bed, and I used miracle layered under the sand to feed the turtle grass (I had seahorses, and they love turtle grass) otherwise the turtle grass would starve. It looked awesome, for nearly a year, until I had a power outage, to shorten the story... I had to open the drapes for light so the seahorses could eat. Hair algae developed within a day, and it was out hand by the end of that day. Once the power returned 3 days later, it was like a wild fire of green hair. I did water changes EVERYDAY... I raised the magnesium (per instruction from somebody on the site who knew what to do to get rid of hair algae) trying to disrupt the algae growth, nothing worked, I had nightmares of hair algae climbing out of tank and choking me in my sleep. Yes it was that bad, I couldn't see the surface of anything in the entire tank, nothing slowed the growth down. I broke the entire tank down and restarted.
It was the miracle mud, it had so many wonderful for plant nutrients that nothing I did could combat the problem. Do you know what plant nutrients are? Phosphates, and nitrates. Yes, miracle mud will make your plants, and nuisance algae grow! However without those nutrients, sea plants like turtle grass can't live for long.
In the end, there is a beautiful macroalgae called Caulerpa Prolifera... it looks like turtle grass, but it doesn't require a deep sand bed, or food. It feeds on the phosphates and nitrates already in the tank, and as I pruned the extra out, I exported the PO4 and NO3 out of my tank.
Now to be honest, seahorses are very messy eaters, if you don't overfeed your regular fish, you most likely wouldn't have my problem. The hair algae was no doubt on the cusp of rearing it's ugly head...the power being out, natural sunlight, and the miracle mud all played a role. All that being said, I still would never do another planted saltwater tank. Decorative macros are beautiful, and they actually help the tank water, making it pristine. Check out "GOLF COAST ECOSYSTEMS" If a macro you like is out of season, wait for it to be in...They have the widest variety of macros I have ever found. Golds, reds and greens, they have them all.