Ocean rocks leeching silicates?

[bitstream]

My LFS has a huge container of dry ocean rocks next to the dry coral skeletons, so I mounted a couple frags to the ocean rocks and dropped them in the tank about 6-8 weeks ago. I’ve had steady diatom blooms. FWIW, the tank is only a few months old, so I’m not entirely sure if the diatoms are still related to the newness of the tank or if the rocks might be fueling the non-stop diatom bloom by leeching silicates.

I’m scraping all the glass 2-3 times a week and the sand looks atrocious.

Could these rocks be leeching silicates, fueling the diatoms?

I asked the store about this today but the folks working there had no idea. Unfortunately I can’t yank these out of the tank just to see what happens unless I want to try to pry the frag discs off the rock and risk damaging the corals, so that’s a last resort.

Anyone know much about putting rocks like this in the tank? They’re dark in color and do sparkle a teeny tiny bit. Upon close inspection, the rocks appear to have some ancient skeletal remains encrusted within.

 

[Miami Reef]

If your source water has silicates, that can be fueling the diatom bloom. Silica is one of the hardest chemicals to remove with RO/DI, and it’s one of the first to leach when the Di resin exhausts.

Rocks and sand can contain silica, but that source rapidly depletes after a few weeks.

Lastly, make sure the algae is actually diatoms and not dinos. They can look very similar.

 

[bitstream]

If your source water has silicates, that can be fueling the diatom bloom. Silica is one of the hardest chemicals to remove with RO/DI, and it’s one of the first to leach when the Di resin exhausts.

Rocks and sand can contain silica, but that source rapidly depletes after a few weeks.

Lastly, make sure the algae is actually diatoms and not dinos. They can look very similar.

I am tempted to grab a Salifert Silica test and check the source water vs tank water. That might give me an indication where the source lies. I get my RODI and saltwater from a LFS, so who knows how well they’re filtering it, though I assume well as I don’t see diatoms in any of their tanks.

I’m sure it’s diatoms as I’ve had them in a freshwater tank in the past… and the culprit back then was indeed a decorative stone high in silicates. Once removed, the issue went away. I’m thinking this could be a repeat, but it’d be odd since the LFS I got them from sells a lot of them to aquarists.

I am positive it’s not dinos.

 

[Miami Reef]

I get my RODI and saltwater from a LFS, so who knows how well they’re filtering it, though I assume well as I don’t see diatoms in any of their tanks.

Not necessarily. In my tank I have a lot of sponges and tunicates in addition to biodiverse live rock. I purposefully dose silicate in my tank and don’t deal with pest diatoms, except for some in my powerheads and other inconspicuous places.

If I added my water to a new tank, it would not take long for it to be saturated with diatoms.

The salifert silica test kit does not work. It shows false negative for many people.

Is the picture of the tank in the first picture how the tank looks now? It looks more than fine.


I personally would not worry about the rock “leeching.” The diatoms will quickly finish the source then leave as long as you don’t keep adding more silica. Sometimes LFS get lazy with their filter replacement, so that’s why I’m skeptical about their water source.

 

[bitstream]

Not necessarily. In my tank I have a lot of sponges and tunicates in addition to biodiverse live rock. I purposefully dose silicate in my tank and don’t deal with pest diatoms, except for some in my powerheads and other inconspicuous places.

If I added my water to a new tank, it would not take long for it to be saturated with diatoms.

The salifert silica test kit does not work. It shows false negative for many people.

Is the picture of the tank in the first picture how the tank looks now? It looks more than fine.


I personally would not worry about the rock “leeching.” The diatoms will quickly finish the source then leave as long as you don’t keep adding more silica. Sometimes LFS get lazy with their filter replacement, so that’s why I’m skeptical about their water source.

The picture is 2 hours after a thorough cleaning. Can post again in a handful of days when it inevitably looks like crap again.

 

[Miami Reef]

In my opinion, the rocks, if they are the culprit of the silica, will stop leaching within 1-2 months of adding it.

If you are still dealing with diatoms, consider checking your water source.

Beware that sometimes dinos can look like diatoms. I know you said they aren’t dinos, it’s just worth noting for the future. They are often mistaken with each other. .

PS. Dinos do not use silica.

 

[bitstream]

I wanted to follow up on this thread. I had 3 rocks in the tank and pulled all but the smallest one. And boom… diatom blooms stopped pretty much immediately.

This tells me that I was right — that at least one of these was leeching silicates and fueling the diatoms.

I had a similar experience with a freshwater tank years ago and after doing some sleuthing, in that case the rock was made up predominantly of silicates.

Word to anyone reading this — if you’re confident your water isn’t a source of silicates, look at the rocks. If they’re comprised of anything other than your usual calcium dry rock, they could be causing some of your problems.

Note that silicates will remain in the water column until used up, so a partial water change will aide in removing excess silicates. I saw a big drop when removing the rocks and doing a 30% WC. Since then, diatoms are minimal to non-existent.

Anyone who thinks rocks magically “stop” leeching after a set period of time is likely incorrect unless you have data to back that assertion. If the rocks are high in silicates, they’ll likely keep leeching. That’s what happened in my FW tank back in the day and I believe history was repeating itself here.

 

[Randy Holmes-Farley]

Anyone who thinks rocks magically “stop” leeching after a set period of time is incorrect. If the rocks are high in silicates, they’ll likely keep leeching.

While you may be correct, I personally am not convinced it is a true statement for actual ocean rocks, and I'm not certain silicate was even the issue, as opposed to phosphate or something else that the pest present was using.

It can also be hard to distinguish diatoms from certain other organisms, except by microscope.

FWIW, if a rock in the ocean (which presumably was there for a very long time) was continually releasing silicate, it would have dissolved, at least to the point where the surface no longer contained silicate minerals.

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[bitstream]

While you may be correct, I personally am not convinced it is a true statement for actual ocean rocks, and I'm not certain silicate was even the issue, as opposed to phosphate or something else that the pest present was using.

It can also be hard to distinguish diatoms from certain other organisms, except by microscope.

FWIW, if a rock in the ocean (which presumably was there for a very long time) was continually releasing silicate, it would have dissolved, at least to the point where the surface no longer contained silicate minerals.

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Silicates are mixed throughout entire rocks, not just on the surface. The small rock I had in a FW tank turned it to be 70% silicates. As soon as I removed that and changed some water, the diatom blooms stopped quite quickly. This was no a coincidence.

And rocks in the confines of an aquarium can leech enough to continually feed diatoms. If the food supply equals or outpaces consumption, the blooms can continue indefinitely.

A rock doesn’t just dissolve overnight. And in the ocean, I’d bet the ratio of water to rocks is high enough that silicates aren’t a massive issue the way the are in a tank.

There are no phosphate issues here as check weekly.

I’m just telling you what I’m seeing with my own eyes. It would not at all surprise me if I re-add those rocks and see diatom blooms again.

 

[Randy Holmes-Farley]

Silicates are mixed throughout entire rocks, not just on the surface. The small rock I had in a FW tank turned it to be 70% silicates. As soon as I removed that and changed some water, the diatom blooms stopped quite quickly. This was no a coincidence.

And rocks in the confines of an aquarium can leech enough to continually feed diatoms. If the food supply equals or outpaces consumption, the blooms can continue indefinitely.

A rock doesn’t just dissolve overnight. And in the ocean, I’d bet the ratio of water to rocks is high enough that silicates aren’t a massive issue the way the are in a tank.

There are no phosphate issues here as check weekly.

I’m just telling you what I’m seeing with my own eyes. It would not at all surprise me if I re-add those rocks and see diatom blooms again.

Your caution for folks who have persistent diatoms to think about rocks and sand is perfectly reasonable and I do not dispute it.

I'm just cautioning the interpretation, and stand by my caution. Our own eyes cannot see chemicals and frequently lead us to misinterpretations of what happened on a molecular level.

 

[bitstream]

Your caution for folks who have persistent diatoms to think about rocks and sand is perfectly reasonable and I do not dispute it.

I'm just cautioning the interpretation, and stand by my caution. Our own eyes cannot see chemicals and frequently lead us to misinterpretations of what happened on a molecular level.

My own eyes have, now more than once, seen a dramatic difference with and without certain types of rocks in two different tanks. And in one case I readded the rock months later only to see a big, persistent diatom problem. Remove the rock, change some water, boom… diatom bloom stops again and doesn’t come back.

And like I said, in that one case I did some sleuthing and found the rock to be made predominantly of silicates.

Whether history is repeating itself in third tank is up for debate, but my eyes aren’t lying. Only way to be sure is to readd the rocks and see if diatoms are a problem again, but I’m not going to bother. Just leaving this info here for future readers to consider. They can perform their own experiments.