Putting crystals in a fish tank can be a beautiful way to enhance the look and feel of your aquatic environment. However, not all crystals are safe for fish tanks. Certain types of crystals can raise pH and hardness levels to dangerous extremes or leach toxins into the water. Proper crystal selection and preparation is crucial to avoid harming your fish.
This comprehensive guide will cover everything you need to know about safely adding crystals to your aquarium. We’ll discuss which crystals are fish safe, how to cleanse and prepare crystals, where to place them, effects on pH and hardness, and much more. By the end, you’ll have the knowledge to design a gorgeous crystal aquascape that thrives.
Which Crystals Are Safe for Fish Tanks?
Not all crystals on the market are suitable for submersion in aquarium water. When selecting crystals, be sure to choose only non-toxic, inert stones that won’t affect water chemistry. The following crystals are generally considered safe:
Quartz
All varieties of quartz, including clear quartz, rose quartz, smoky quartz, citrine, and amethyst, are inert and fish safe. Beautiful quartz clusters can make impressive statement pieces in an aquarium.
Fluorite
This colorful mineral comes in a wide array of hues like blue, green, purple, yellow, and rainbow. Fluorite is soft and won’t alter water parameters.
Aragonite
Commonly used as substrate, aragonite helps buffer pH and hardness. Its white coloration looks nice as accent stones.
Petrified Wood
Petrified wood adds neutral earthy tones to a tank. Avoid types with bright colored agate fillings, as these could leach into water.
Granite
Polished granite pebbles and columns add striking sparkles. Opt for neutral colored granite rather than red, which could stain water.
Marble
Both natural and cultured marble pieces are safe if pH neutral. Don’t use acidic types like vinegary limestone.
Obsidian
This natural volcanic glass has a beautiful jet black color. Use nuggets and shards sparingly, as obsidian can have very sharp edges.
Slate
Neutral colored slate rocks and chips work well. Avoid glittery mica slate that could flake.
Crystals to Avoid
On the flip side, the following types of crystals and stones are toxic for aquarium use and should be avoided:
Malachite
This vibrant green copper mineral is hazardous to aquatic life. It can leach toxins into the water.
Lapis lazuli
While beautiful, lapis contains high levels of pyrite and calcite that can detrimental to water quality and pH.
Salt crystals
Crystals like halite are water soluble and will rapidly increase salinity.
Calcite
Though pH neutral itself, calcite will readily dissolve in water, leading to heightened alkalinity, hardness, and pH.
Gypsum
Another water soluble mineral that can spike calcium and sulfate levels. Avoid selenite, satin spar, desert rose and other gypsum stones.
Galena
Galena contains lead, which can leach into the tank and poison your fish.
Chrome diopside
This chromium bearing crystal can release the toxic heavy metal into water.
Any crystal with heavy metal content, including cadmium, nickel, or copper
Heavy metals, even in trace amounts, can build up and kill fish. Completely avoid any suspect stones.
Dyes, paints, or treatments
Avoid artificially colored or treated crystals. Chemical residues could enter tank water.
Sulfur bearing stones
Sulfur compounds become highly acidic when submerged, lowering pH. Avoid crystals like pyrite.
Radioactive specimens like uranite
Radioactive crystals emit dangerous ionizing radiation and radon gas. Never put in an aquarium.
Soluble stones like salt, calcite, gypsum
Soluble minerals will dissolve, altering water chemistry and clarity.
When in doubt, it’s best to avoid a crystal rather than risk it harming your fish. Opt for known inert stones.
Table: Safe and Unsafe Crystals for Fish Tanks
| Safe | Unsafe |
|---|---|
| Quartz | Malachite |
| Fluorite | Lapis lazuli |
| Aragonite | Salt crystals |
| Petrified wood | Calcite |
| Granite | Gypsum |
| Marble | Galena |
| Obsidian | Chrome diopside |
| Slate | Stones with heavy metals |
How to Cleanse and Prepare Crystals Before Adding to a Tank
Before placing stones in your aquarium, it’s important to properly cleanse and condition them beforehand. This removes any possible contaminants and readies them for submersion. Here are some tips:
Wash thoroughly
Give crystals a good scrub under running water to remove dirt, dust, or residue. Use a toothbrush to clean in crevices.
Boil quartz crystals
For transparent quartz specimens, boil 5-10 minutes to sterilize. Other harder minerals can skip this step.
Degrease with soap
Use dish soap and an old toothbrush to break down oils, skin residues, or manufacturing chemicals.
Vinegar test
After scrubbing, soak crystals for an hour in white vinegar. If it fizzes, that means the stone is calcite-based and unsafe.
Rinse well
Thoroughly rinse all soap or vinegar off until water runs clear. Allow to dry fully before adding to tank.
Check for sharp edges
Smooth any pointed corners or shards, especially with brittle stones like obsidian, to prevent injuries.
Be diligent about properly preparing crystals before adding them to your aquarium. It’s better to take these precautions rather than mistakenly introduce something harmful into your tank.
Where Should You Place Crystals in an Aquarium?
Where you position crystals in a tank can impact both aesthetics and safety. Follow these tips on crystal placement:
Base of tank
Larger crystals look nice arranged at the bottom of a tank as a decorative base layer. This prevents accidental ingestion by bottom-dwelling fish.
Supported by substrate
Partially bury smaller crystals in the substrate, either sporadically or in groupings. This helps prevent dislodging.
Above substrate
Rest smaller crystals atop the substrate for visibility and sparkle. Avoid loose small crystals that could be swallowed by fish.
Anchored to decor
Affix crystals to tank decor like driftwood or rocks using aquarium-safe silicone. This allows positioning anywhere.
Away from caves
Don’t put loose crystals near cave decor where fish could try to ingest them.
Distributed evenly
Aim for even coverage across all areas of the tank. Don’t overload any one section.
Not overpowering
As accents, crystals should enhance the aquatic layout, not overwhelm it. Less is often more.
Visible from front
Place the most decorative crystals where they can be admired through the front viewing pane.
Avoid equipment
Keep crystals away from intakes, outlets, heaters, and filters to prevent obstruction and damage.
Take the time to thoughtfully arrange your crystals in optimal spots for both safety and aesthetics.
How Crystals Affect pH, Hardness, and Chemistry
Adding crystals can potentially influence water parameters like pH, hardness, and mineral levels. This depends on the crystals in question:
Quartz is inert
Clear quartz and all its varieties have a neutral pH and won’t alter water chemistry whatsoever. It’s completely inert.
Fluorite adds hardness
Fluorite does slowly increase overall water hardness to some degree. Its effect is mild.
Aragonite buffers pH/hardness
Introducing aragonite sand or stones can help buffer pH and general hardness. This makes it more stable.
Calcite raises pH/hardness
As mentioned, calcite rapidly dissolves and spikes carbonate hardness and pH. Avoid this stone.
Gypsum increases calcium and sulfate
Soluble gypsum crystals will dissolve and boost calcium and sulfate concentrations.
Heavy metals accumulate over time
Even trace metals slowly build up. Have water tested if using crystals containing copper or other metals.
Other soluble crystals raise salinity
Salt, mica, pyrite, etc will increase total dissolved solids and salinity with dissolution.
Overall, quartz and fluorite are extremely safe. Aragonite can be beneficial. Avoid all soluble or toxic crystals that alter water chemistry. Test levels periodically if concerned. Making smart crystal choices will maintain a healthy environment.
Using Crystals with Sensitive Species
Certain aquatic species are more sensitive to changes in water chemistry than others. Take care when selecting crystals if housing:
Freshwater shrimp
Dwarf shrimp need stable pH and hardness. Quartz or fluorite are better than aragonite, which buffers more aggressively.
Tetras, rasboras, or other soft water fish
Soft water species prefer lower hardness and neutral pH. Completely inert quartz has less impact.
Bettas and gouramis
Anabantoids thrive in soft, acidic conditions. Quartz or slate suit them better than minerals that raise hardness and pH.
Scaleless fish
Loaches and catfish lack protective scales. Fluctuations in chemistry negatively impact their osmoregulation.
Wild caught fish
Fish sourced from very soft, acidic waters will be adapted to specific conditions. Dramatic shifts in hardness or pH could stress them.
Fry or juveniles
Young fish are still developing tolerance for parameters. Limit use of stones that alter water chemistry.
While most healthy adult fish can adapt to some changes, take a conservative approach with sensitive species or life stages. Know your species’ needs.
Top 5 Fish Safe Crystal Choices
If you want beautiful, worry-free aquarium crystals, you can’t go wrong with these 5 inert, non-toxic options:
Clear Quartz
Abundant, affordable, and completely neutral for all setups. Great for beginners.
Amethyst Quartz
Gorgeous purple hues. Amethyst is simply quartz tinted by trace iron. Completely inert.
Rose Quartz
Radiates calming pink vibrations. Entirely stable for any aquarium.
Fluorite
Vibrant fluorite comes in endless color varieties. Mildly hardening.
Obsidian
Natural volcanic glass with striking blacks. Use judiciously due to fragility. Smooth edges well.
Any of these five fish safe crystals can beautifully enhance your tank. Have fun selecting stones that speak to you visually and spiritually.
Conclusion
Adding the right crystals to a fish tank can take it to the next level visually. Sparkling stones complement aquatic layouts beautifully. With proper selection and preparation, crystals can be incorporated safely into freshwater and saltwater aquariums alike.
Focus on non-toxic, stable options like quartz, fluorite, aragonite, slate, and petrified wood. Completely avoid soluble, radioactive, or heavy metal bearing stones that could compromise water quality and health. Place crystals thoughtfully, distribute them evenly, and anchor them securely. Understand how your choices impact pH, hardness, and chemistry, especially for sensitive species.
With the guidance above, you can now design a stunning crystal aquascape that keeps both fish and crystals thriving harmoniously. This fusion of nature and element brings good energy into any space.
Frequently Asked Questions About Crystals in Fish Tanks
Can I put any crystals in my tank
No, only certain crystals are suitable. Avoid soft, water-soluble, radioactive, or toxic specimens. Stick to inert, non-porous crystals that won’t affect water chemistry.
What’s the safest crystal for fish tanks
Clear quartz, including amethyst and rose quartz. The quartz family is completely inert and has no effect on pH, hardness, or chemistry.
Should I glue crystals to decor
Yes, firmly affixing crystals with aquarium silicone prevents loose stones that could be accidentally swallowed by fish.
Can crystals alter pH or hardness
Some mineral crystals like aragonite and fluorite can mildly influence pH, hardness, and mineral content over time. Significant shifts indicate dissolving – remove any suspect stones immediately.
Will crystals leach anything into the water
Non-toxic crystals like quartz or granite will not leach substances. However, some crystals like malachite or lapis lazuli can release copper, sulfates, or other elements over time.
Can I incorporate crystal grids
Yes, creating crystal energy grids underneath tank substrate is believed to impart positive energy. Just don’t use any water-soluble crystals in the grid itself.
How often should I remove and clean crystals
Remove and clean crystals during any routine tank maintenance, about once a month. Use this time to inspect for any damages or issues.
Do crystals need to be cleansed after removing from a tank
Yes, always re-cleanse crystals after removing from an aquarium the same as you did before first adding them. This removes accumulated organic matter.
Are crystals safe for saltwater tanks
Inert, non-porous crystals are generally safe for saltwater, however salt creep can gradually coat and adhere to them. Remove and clean crystals frequently to minimize this.
Can I put heated crystals like lemon quartz in tanks
No. Heated, irradiated, or treated crystals were likely exposed to toxins. Their safety for submersion is uncertain. Always stick to natural specimens.