Solving Bryopsis Problem

[RockyBoy]

This Thread I 've got from Reef Central on how to rid of your bryopsis....

Bryopsis Thread from Reef Central

For those who can't access .. I've cut and paste below....

Finally an easy solution to bryopsis!

I've battled for many months against this vile weed. Nothing I tried would eat it. I tried lettuce sea slugs (they eat it but not fast enough to control it), sea hares (aplysia sp.), almost every kind of snail commonly available in the hobby, 3 kinds of dwarf hermit crabs, emerald crabs, a small blue lined rabbitfish. Only the lettuce sea slugs ate it, but they only suck the chloroplast out and the plant still grows fine despite this. Plus they are easily killed by even the weakest of powerheads. I couldn't keep them alive in my main system due to the filtration and current.

Everyone kept saying there must be a nutrient problem or bryopsis wouldn't grow. This sounds good at first, but makes no sense when tests consistently show 0 nitratres/phosphates and you have a refugium with chaetomorpha growing. Cheato should eat up the nitrates/phosphates and keep your tank clean, right? My chaeto was getting choked out by bryopsis. Bryopsis needs extremely little light and nutrients to get by, even less than chaetomorpha needs. If a healthy tank (low nutrients) allegedly can not sustain bryopsis, then how is it logical to believe the same system can sustain chaetomorpha? Lowering nitrates/phosphates was not an option. I started using a phosban reactor, but how do you reduce phosphates beyond zero? This was a wasted investment, but at least it was cheap.

Then I stumbled on to this thread at Reef Frontiers. Mojoreef suggested boosting magnesium to 1500-1600. I don't understand the chemistry behind this, but for some reason the bryopsis absorbs the magnesium and it prevents it from growing. I didn't believe it at first, it was too easy. But it was cheap, so I gave it a shot. I ordered some Kent Tech M. I already had a magnesium test kit, and my mag always measured somewhat low (around 1100). I started boosting it up and within days the bryopsis turned translucent yellowish brown and started falling apart. I accidentally overshot my goal of 1550 magnesium and went to 1680ppm. Here are some day by day snapshots starting when the magnesium reached 1680:

Day 1

Day 2

Day 3

Day 4

I later regretted picking this spot in the tank to document the bryopsis decline because the rock is covered with green zoanthids underneath the bryopsis. So as the bryopsis dies and falls off the rock, it still looks green on the rock, but it's the zoanthids you're seeing now, not the bryopsis.

At the same time, chaetomorpha in my refugium looks dark green and healthy. The bryopsis that was choking it is now all mushy and yellow.

I'll continue to update this thread with pics of my dying bryopsis if there's interest