Silicates Leaching From Rock Causing Diatoms?

[jcol]

Hey guys, long time reader here but I think this is my first post.

Here's the situation. I have a Nuvo 40 that's 5 months old. 3 months in I started seeing diatoms covering all my rock. Only the rock, not the sand. I KNOW they're diatoms, not anything else. I've educated myself on difference between diatoms/dino/cyano/etc. When I first got them I just waited and did nothing, as most people suggest for a new tank with diatoms, but now it's been two months and I fear I might have a bigger problem.

Here are my water parameters:
Ammonia: 0
Nitrite: 0
Nitrate: <4
Phosphate: 0
Calcium: 450
Alkalinity: 9.5
Temp: 80
Salinity: 1.025
Silicate (yes I tested): 0

I'm using RODI water with zero tested silicate.
I'm using HW Wiegandt Reefer salt with zero tested silicate.
I do weekly 5 gallon water changes.
I have two skimmers as well as two refugiums in the back of the Nuvo 40.
I have a solid clean up crew with ceriths, nerites, trochuses, and hermits.

I've done a bunch of research on this and the only plausible hypothesis I have is that my rock is slowly leaching silicate, and feeding the diatoms on the rock. The rock I purchased was dry rock from my LFS, it came in a 50 lb box I believe, but I can't remember the brand. I remember it being similar to Reef Saver rock, because it's mined from the earth and doesn't come from the ocean. I've heard rumors of reef saver rock leaching silicates. I don't know how true this is.

So with all of this information, what do you guys make of the situation...? You think the rock could be leaching silicate, or is there another explanation I'm missing? If the rock IS leaching silicate, do you think it will stop eventually, or should I just replace the rock? I have some fish and coral so this would be a hassle, but I'd do it if necessary.

Let me know what you think.

 

[jcol]

Update on this. I found a picture in my phone of the box the rock came in. It's Carib Sea South Seas Base Rock. Anyone ever have issues with this rock?

 

[SAT]

Jcol,

[Welcome]

It would surprise me if Carib Sea rock leached silica, but stranger things have happened.

About diatoms... of all the types of nuisance algae, this is about the least obnoxious. If there is light and any nutrients in the water, and there are always nutrients in the water, regardless of what your test kit says, you will get some amount of algal growth. My advice: get some snails and be happy it's only diatoms.

 

[Clavius78]

Wow, this sounds like my situation, only bottom and rock switched around.

I just replaced my Caribsea live sand because the sand was leaching silicate in June. My sand, and only my sand, was always covered in diatoms. For years! And I don't agree with the previous poster. It's ugly!

When I tested my aquarium-water for silicates the test kit would always test 0 / undetectable. And so would the water from my ion exchange unit. It wasn't until I took a sample of the brown-covered caribsea sand and water, stirred it really very hard and tested that brownish sample, that I found a positive reading for silicates.

I replaced it with really coarse bright white sand from ATI. Had a little mini-startup in the beginning. It turned brown as well, so I thought "oh no! here I go again." But after two months it cleared up. For the first time in 8 years my bottom is shiny white, reflecting light up against my corals. Just a shame that it took so long for me to solve this puzzle.

 

[jcol]

Jcol,

<img src="/images/welcome.gif" width="500" height="62"><br><b><i><big><big>To Reef Central</b></i></big></big>

It would surprise me if Carib Sea rock leached silica, but stranger things have happened.

About diatoms... of all the types of nuisance algae, this is about the least obnoxious. If there is light and any nutrients in the water, and there are always nutrients in the water, regardless of what your test kit says, you will get some amount of algal growth. My advice: get some snails and be happy it's only diatoms.

It would surprise me too, as they're a pretty reputable brand. What worries me is there has been some documented scientific evidence of diatoms harming montipora in the wild, so I wouldn't say they're completely harmless.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3412319/

I do have a bunch of snails (nerites, ceriths, trochus), but they seem to prefer the glass or sand bed more than the rocks.

 

[jcol]

Wow, this sounds like my situation, only bottom and rock switched around.

I just replaced my Caribsea live sand because the sand was leaching silicate in June. My sand, and only my sand, was always covered in diatoms. For years! And I don't agree with the previous poster. It's ugly!

When I tested my aquarium-water for silicates the test kit would always test 0 / undetectable. And so would the water from my ion exchange unit. It wasn't until I took a sample of the brown-covered caribsea sand and water, stirred it really very hard and tested that brownish sample, that I found a positive reading for silicates.

I replaced it with really coarse bright white sand from ATI. Had a little mini-startup in the beginning. It turned brown as well, so I thought "oh no! here I go again." But after two months it cleared up. For the first time in 8 years my bottom is shiny white, reflecting light up against my corals. Just a shame that it took so long for me to solve this puzzle.

This worries me as I have Caribsea sand as well! Although no diatoms so far on the sand bed. You gave me an idea to take a water sample from inside one of the crevices of the rock though to see if it tests positive for silicate. I'll post the results when I do this.

 

[jda]

It is more likely that it is phosphates that are coming from the rock, but there could be silicates. Aragonite binds with phosphates to equilibrium with the surrounding water - it is a little more complicated than this, but this works for now. Dry rock that is mined is usually bound full of terrestrial phosphates from the water than ran through it eons ago - nearly all of this has it. Depending on how bad it is, it could take months or even years go all leave and you will have to be aggressive with export.

Does your water test any phosphate? It might not where the stuff on the rocks is consuming all of it upon export. If the level is high and/or climbing, then you need to start with some export.

Most sand is from the ocean and is phosphate free (mostly) since the area is so oligotrophic and starved for nutrients. Real live rock from the ocean is this way too... even though it costs a little more, it is a bargain in the long run since the box of phosphate-bound dry rocks does not consider the price of waiting and all of the water changes and GFO that it will take to get the phosphate out.

 

[Lsufan]

Something u can try is taking a rock or two & putting in a bucket with freshly mixed saltwater. I would use a lid so no light gets in. Let it sit a day or two & test that water. If the water has po4 or silicates then the rock is leaching it. If not then u know that isn't it. The problem with testing the tank water is the diatoms or algea takes in the nutrients as fast as it leaches out of the rock.