Fish-safe?

[TylerFerretLord]

I was wondering if the following were safe to place in a tank.

-Bricks
-Concrete
-Twigs (from oak or dogwood trees)
-Glass bottles
-Ceramic, glazed and not
-Plastic bottles

You're probably thinking I'm mental now, but I've had an idea to decorate a tank with odd materials for a while.

 

[Piltdownpaul]

Plastic will decompose unless you are sure its safe-concrete is a definite no no-it will have lime in it making your water hard and alkali.

 

[Lateral Line]

Bricks, almost certainly okay. There are some specialist bricks, but I doubt you mean these.
Concrete, even old concrete is likely to be alkali. It will likey raise hardness and pH, depends what you are keeping. There are other issues with concrete - best avoid.
Twigs, Oak, Beech, most hardwoods no problems but in small enclosed systems, fresh, not recommended, use old well dead well soaked pieces.
Glass and ceramics, usual comment on sharp edges, but are mostly inert.
Plastics, stuff suitable for food should be fine.

 

[three-fingers]

-Bricks Depends, I think there are lot's of slightly different types of bricks with different minerals used for colour and consistency, to be safe I would say no unless you can find out exactly what went in to making it and that everything was fish safe. I've been told by and lfs in the past that 'bricks' have lime in them too.
Having said that I have seen old looking red bricks in large tanks before with plecs, and everything seemed fine.
-Concrete Would raise the pH a lot. Some people make live rock out of it for reef tanks though. I think concrete has contaminants in it and you need to treat it somehow to get these out, I'll have a look see if I can find a link with a how-to. Here we go, it was the lime that needed removed. Although in that link it was a more pourus mix that was used - plain concrete would take longer or maybe be impossible to get the lime out of.
-Twigs (from oak or dogwood trees) Don't know about dogwood, but oak twigs are certainly fine if they are dried (any sap left in them will usually lead to fungus). I'd leave s them to soak to leach out possible contaminants if they are from the side of a busy road or in a city though, for some reason it's also recommended the bark is scraped off too.
-Glass bottles Yes.
-Ceramic, glazed and not Yes, and it depends what it's glazed with - I'm no expert on ceramics but there's probably loads of different glazes. Some aquarium decorations are glazed though, so some must be OK.
-Plastic bottles If they are from a drinks bottle meant for human consumption, yes they should be ok.

 

[TylerFerretLord]

Thanks.

I never planned on broken glass, just bottles and vases and such.

For the twigs, can I take a few fresh pieces and leave them in a closet or something for a month or so? Is there any way to dry them out?

 

[TylerFerretLord]

OK, I just remembered something else.

Are shells OK? My mother has a collection. I know they'll grow algae, but I'm getting snails and shrimp.

 

[three-fingers]

Shells would raise the pH too, good for snails and shrimp, but some sensitive shrimp (like crystal red shrimp) don't fare to well in such alkaline water due to nitrogenous waste being more toxic at high pH.

 

[TylerFerretLord]

I was only really planning on going for cherries and greens honestly, so it's not that big of a problem.

Would the tannins from bogwood counteract the rise in ph?

Thank you again.

 

[three-fingers]

Should do, but after water changes the tannins will disappear while the shells/concrete ect will pretty much be raising the pH until they have dissolved completely.

If you want a planted tank you could also use pressurised CO2 to lower and control the pH.

 

[TylerFerretLord]

I thought that shells and such only dissolved when the ph fell below a certain point? And would a shell or two raise the ph by any significant amount anyway?

I'm only planning on getting low-light plants(moss, java-fern, crypts), no CO2 for me.

 

[three-fingers]

A shell or two would barely make a difference, but along with concrete and bricks there would be a noticeable increase. Depends on the carbonate hardness (buffering capacity) of your water too.

Shells dissolve faster at a lower pH, but still dissolve at a pH above 7, raising it further. Shells are mainly made of calcium carbonate, as are things like tufa rock and some of the components of concrete.
I'm not very good at chemistry (predicted a B in higher and got a C on the last test ), and there are loads of possible reactions calcium carbonate can be part of in our aquariums, but to me the important basic thing seems to be that some of the poorly soluble calcium carbonate - CaCO3 - dissolves and dissociates into CO3(2-) and Ca(2+) ions when placed in water. Some of these CO3(2-) ions combine with the H+ ions in the water to make bicarbonate, which counts towards the KH - making the water more resistant to pH change. The H+ ions are being used up, and since the pH is a measurement of H+ ions compared to hydroxide ions (with more H+ ions than hdroxide ions being acidic and vice versa), this raises the pH.

Calcium carbonate also reacts with carbon dioxide and water in our aquariums to make calcium bicarbonate - which exists in equilibrium with Ca2+ ions and bicarbonate so this also raises the KH of the water.

There are always going to be some H+ ions and carbon dioxide in our aquariums, a pH above 7 simply means there are less of them - but the reactions still happen, just at a different rate . It's all about equilibrium.

Tannins and stuff do lower the pH - I don't know the exact chemistry behind that - but they leach out of the wood and are removed over time with water changes. So it really depends on how much things you have in them with calcium carbonate in them compared to things that soften the water and lower the pH as to what your pH will be.

Lol I know none of that really needed to be explained, but I count that towards my chemistry revision for my NAB on Friday and prelim on Monday...then final exam in a few weeks .

If shells only dissolved below pH 7 - how would you ever get to pH 8 in an aquarium?