May 24, 2007
On Rocks in Aquariums
So I spent some time this week trying to figure out how I ultimately want to decorate my fish tank. All of the tanks that I really like are about 50 - 1000 gallons and full of large plants, rocks, and twisted drift wood. Good for abstract inspiration, but not so helpful for directly inspiring a design for my tiny little 10 gallon tank.
Anyway I think I've decided that I'm going to need some rocks (hopefully with some crevices and caverns) as well as some drift wood and tall plants (good for tetras to hide in). I have barely started my research into plants, but I think I've pretty much finished my research in to rocks. The very concise answer is, most rocks that aren't metallic or full of calcite are okay. Random non-aquarium rated plastic is a no-go because it can leech all sorts of weird and toxic things into the water over the long term (this makes me sad because I wanted to put dice in there). Glass is okay so long as it is not colored with metallic pigments (I think).
I was particularly curious about semi-precious stones, since I've been casually collecting various semi-precious stones and fossils for the last 15 years or so. Some of the stuff I collected when I was 11 sucks, but it's a collection none the less.
I got most of my information on particular types of stone and semi-precious stone from this very nice summary page. It collects a bunch of separate advice posts from various people/places. There's a lot of info there, but it is not very concise and some things are repeated with similar but not identical advice.
I decided to condense that page into the following outline of rock tips (if you have questions don't ask me, go read the original page and contact the folks who gave the advice in the first place):
GeneralGood Stones
- if a drop of vinegar makes it bubble, it's no good because it contains calcite
- avoid things that are veined with metal or look metallic
- (silicon may be used to attach things? I wasn't really clear on this...)
- an autoclave can be used to make driftwood sink sooner (and sterilize it)
- wash things that will go in the tank thoroughly, scrub with dedicated brush that has never touched harsh cleaners/chemicals
Bad Stones
- slate/shale
- sandstone (natural, test for calcite)
- granite
- lava rocks (try home depot or other garden stores)
- onyx (but not "Mexican onyx", which is a different mineral with lots of calcite)
- quartz
- microcrystalline varieties like:
- Agate - Banded variety
- Carnelian - Reddish, transparent to translucent variety
- Onyx - Banded variety in which the banding lines are straight and parallel, and consistent in band size.
- Jasper - Opaque variety of Chalcedony that occurs in all colors.
- Tiger's Eye - Pseudomorph of Quartz after fibrous Crocidolite.
- Chrysoprase - Apple-green variety
- Bloodstone (or Heliotrope) - Dark green to greenish blue variety dotted with small, red, bloodlike spots.
- Sard - Brownish to brownish-red, transparent to translucent variety
- Sardonyx - Banded variety with straight parallel bands of brownish to red alternating with white or black bands.
- Flint - Massive, uniformly colored variety that is somewhat impure
- crystalline varieties like:
- Amethyst - Purple variety
- Citrine - Yellow to yellow-brown variety
- Rose Quartz - Pink variety
- Rock Crystal - Colorless, transparent variety
- Smoky Quartz - Brownish-black, "smoky" variety
- Milky Quartz - White, translucent to opaque variety
- Rutilated Quartz - Quartz with golden-yellow, needlelike Rutile inclusions
- Aventurine - Opaque, massive Quartz containing small mica, Hematite, or Goethite scales which cause a glistening effect.
- "zebra rock", a quartz agate
- petrified wood (quartz type)
- jade
- round river stones (not sure about the exact content of the stones here?)
- marble
- limestone
- dolomite
- pyrite (will oxidize and cause acidic water)
- shells
- any fossils
- coral skeletons
- sandstone (testing positive for calcite)
- anything metallic
- coal
- geodes (may contain calcite)
- gypsum (will dissolve, can be identify by softness)
- this includes varieties like:
- alabaster - fine-grained and usually white or pink
- satin spar - shimmering white or pink parallel fibers, usually filling a vein in other rocks
- selenite - a clear crystal and can be very large
Incidentally, if anyone knows whether or not tourmaline is okay to put in an aquarium. I have a lovely piece of tourmalated quartz that I'd really like to put in if it's safe. As far as I can tell tourmaline is mostly silica, so the only danger would be from metal ions that are part of it's make up. Sadly, my chemistry left me long ago, so I don't think I can figure its solubility out myself.
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