# Rock Wool Slab as Substrate



## JeffLL (Oct 20, 2006)

Please see my profile for a fuller descript of my paludarium.

I am rebuilding the tank, 75g, 48w, 18d, 21h, for the third time. I keep crayfish as scavengers. Unfortunately, they like to rearrange the 'furniture', digging up whatever I plant. In an effort to make the tank more interesting I have created a terrace from Grodan Rock Wool, from which to grow the background. The front face of the slab is hidden by a wall of granite rocks which will also serve to keep the standard gravel from easily migrating off the terrace. The rock wool slab is also there to provide an alternative for the roots other than the UGF (my choice, live with it), as well as a method of removing an offending plant, roots and all.

Light is two T-8 "sunlight" bulbs, not grow bulbs, but sunlight as opposed to cool white. As a paludarium (half aquarium/half terrarium) the water level will be little more than 12". The background plants will end up emersed, as might a showcase plant or two. The 'aquarium' portion will be somewhere around 25g of water for comparison 30w, 18d, 12h. A few SAEs (once I find them) will replace a pleco as algae control. 

I want easy! Cheap too!!! And tolerant of wide pH and temp. Oh, not too tasty would be nice. Not too tall too, I like bushy backgrounds. What do you all suggest? 

Are there any horror stories with rock wool, a.k.a. stone or mineral wool? 

What else should I be doing for micronutrients, if anything? I am using expanded lightweight clay aggregate (Hydroton brand LECA), as the land mass so I do not expect to suffer from iron deficiency, or a lack of CEC. Note that the LECA is 'live' within the circulating water column. I like to bury two pennies, one old copper, one newer zinc. I have no plan to use CO2, and if I did, yeast and sugar will do just fine from a cola bottle.

Thank you, in advance, for your help.

JeffLL


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## yxberia (Apr 19, 2005)

Rock wool is a source of phosphate which is the source of algae.


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## hoppycalif (Apr 7, 2005)

yxberia said:


> Rock wool is a source of phosphate which is the source of algae.


Please, don't spread that misinformation. Phosphate is not the source of algae. In a tank with normal ranges of nutrients in it you can double or triple or quadruple the amount of phosphate and it will not cause algae. Various algae are encouraged to grow by several things, but phosphate isn't one of them.


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## MatPat (Mar 22, 2004)

hoppycalif said:


> Phosphate is not the source of algae. In a tank with normal ranges of nutrients in it you can double or triple or quadruple the amount of phosphate and it will not cause algae. Various algae are encouraged to grow by several things, but phosphate isn't one of them.


I have to agree with this. On a couple of occasions now I have mistakenly added upwards of 6ppm of PO4 to my tanks without causing an algae outbreak. The only way I can see PO4 causing an algae outbreak is when it causes the plants to use up the NO3 faster than what it is added. I guess this can be an indirect effect of adding too much PO4 but it was still the lack of NO3 not the excess PO4 that caused the algae, at least in my case.


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## redstrat (Apr 3, 2006)

a lack of phosphate will be more likely to cause algae growth then an excess of phosphate. GSA is a perfect example of this, if you see it show up dose some phosphate and watch it dissapear. Other algaes could also take hold when the other nutrients aren't being used by the plants because there is a lack of phosphate. 

:deadhorse 

anyway... back to rockwool in the aquarium. I have received aquatic plants grown in rockwool in the submersed form. The only problem I can see is it would be much harder to rearange your plant arangement because the roots really get into rockwool. It might also be a mulm magnet, I could be wrong about that as I haven't used it myself. 

just my two cents.


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## JeffLL (Oct 20, 2006)

davis.1841 said:


> The only problem I can see is it would be much harder to rearange your plant arangement because the roots really get into rockwool. It might also be a mulm magnet, I could be wrong about that as I haven't used it myself.
> 
> just my two cents.


The intention is for a stubborn substrate that resists the crayfish. If I end up tearing out the rockwool, so be it. I certainly have enough of the stuff to be able to cut out a hunk and replace it. However, you have given me reason to think very carefully about placement.

As for being a mulm magnet, why do you think so?

Also, what would make mineral wool a phosphate source?


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## yxberia (Apr 19, 2005)

hoppycalif said:


> Please, don't spread that misinformation. Phosphate is not the source of algae. In a tank with normal ranges of nutrients in it you can double or triple or quadruple the amount of phosphate and it will not cause algae. Various algae are encouraged to grow by several things, but phosphate isn't one of them.


Thanks for pointing out. Most (I think all) of the aquarium product/fertilizer claimed they have no phosphate thus does not cause algae. Do you have any good reference that claim the otherwise ?
However, I'd go back to study on this.


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## Laith (Sep 4, 2004)

yxberia said:


> Thanks for pointing out. Most (I think all) of the aquarium product/fertilizer claimed they have no phosphate thus does not cause algae. Do you have any good reference that claim the otherwise ?
> However, I'd go back to study on this.


You do have several "enlightened" companies that actually have fertilizers for aquarium plants that contain P (and N): Seachem, Kent... and now Tropica. I heard recently that even Dennerle has woken up to the fact that plants *need* P.

My best reference has been trying it out. In a well planted, well lit, CO2 injected tank with good nutrient levels, add 5-10ppm of PO4 and you will not get an algae bloom (you could probably add more but I've never personally gone that high). As mentioned, you need to watch your NO3 levels as plants starving for P that suddenly get it can easily eat up all the N available.

If you do this experiment and you do get an algae bloom, it's probably a good indication that something else is deficient in the tank...


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## redstrat (Apr 3, 2006)

I think all the hype about not allowing any P to enter the tank comes from Marine Reef Tanks, where pretty much anything Nitrate, Nitrite, Ammonia, Phosphate are all supposed to be as close to 0ppm as possible. The reasoning is not only for fear of algae (which P can cause in marine tanks somehow or at least it did for me) but for the health of the corals/inverts ect... At least this was the thinking years ago when I was really into reef tanks. I know that now they go so far as adding refugiums which are basically saltwater planted tank that is connected to the main show tank that's sole purpose is to remove N and P in the water. They also use RO-DI water instead of tap water to remove any traces of these chemical or others.

JeffLL - the only reason I said anything about it possibly being a mulm magnet is because rockwool seems to have a lot of internal open spaces and crevases like a sponge, any waste that gets caught in it, if not absorbed by the roots could be suck there to rot... just a theory. I've never tried rockwool or anything like it for more than just a quick temporary thing so I really dont know if any of that is true. Just a concern I would have I guess... I'd say go for it though, it seems like the perfect solution for the problem your having.


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