A. Grandis
Active member
In my experience any zoanthid with cyano or algae on it will be irritated and not open. In the pictures it looks like all of yours have some cyano on them. Try to brush them off a bit and solve your cyano/algae issues. Removing the sand will probably help with this a great deal. (See below.)
I agree that the sand is a problem. The package says it is polymer coated, which means that the grains have been covered with an artificial substance (like resin) to give it the black color. These substrates are usually used for freshwater though they often claim to be safe for saltwater. Not only does the coating often wear and rub off, but the sand that they started with is silica which is not what you want for a reef. Silica feeds things like diatoms. So even if it has pictures of saltwater fish and claims to be safe for saltwater, that doesn't mean it's good for a reef (fish only would be fine, but you'd still get algae). I would remove it bit by bit from both of your tanks and replace it with something more appropriate, like aragonite. You can also leave them bare bottom if you prefer. Good luck!
:thumbsup:
Before I used to believe in brushing the polyps, but not anymore!! I wouldn't brush the zoas for nothing nowadays. I almost lost a great colony of Zoanthus sp. once after brushing algae off with a very soft toothbrush with extra gentle strikes. Never again! It could do some internal/external damage/irritation and even open the way for an infection. Besides the use of brush won't remove all the algae anyway.
The best thing to fight against algae and cyano is really correct the water chemistry, mainly removing organics. Skimmer!!! Water changes in a regular maintenance schedule and good lights. They'll be aways there, but if the system is under control they shouldn't be a problem. The use of activated carbon is a choice and could help in many cases. I would avoid the use of activated carbon in a system with zoas, unless it really needs to be there to fix a problem. Best would be the ones with insignificant rates of phosphates, like Chemi-Pure or the Premium ROX 0.8 from BulkReefSupply.
The siphoning of cyanos can be done with an air line while doing partial water changes and many times it is so easy to export that way because the cyanos aren't really attached to the polyps, but they lay on them, covering, loosely. Different than many types of algae.
Talking about the substrate again...
Actually I would prefer to believe that silica substrate wouldn't offer significant amounts of silica to the water to the point for a diatom bloom. BUT, when the silica substrate is exposed to very low pH, in the presence of organisms releasing organic acids, the direct contact with silica sand would be dissolved slowly, yes. Again, as far as I know that is insignificant in many cases. There are many different types of silica sand from many different environments. Some would have more dissoluble silica than others. Some would have more "impurities" than others and that would help/retard to the amount of silica dissolved, besides the variables among different types of systems.
It is although very wise to avoid silica sand!!!!
In another hand, in this case, the chemicals used to coat the silica sand are junk!! Also, the presence of heavy metals are found in many other types of the dark substrates available. Even if there is no coating on them! Aragonite is much better, releases much less silica and looks good and clean too.
Not a flaming, just adding to it with MOE, my friend!! :thumbsup:
I kinda like this subject.
Grandis.
your tank setup sounds similar to mine except I have a lot of flow. I do not like the look of bare bottom also. I too stopped tested my water bc I do routine 15% water changes every week so that shouldn't be a problem. I did test when algae started showing up and everything showed up like it normally does. Sounds like you have a good color combo on your tank to make the corals colors pop! 
