Guest Post By Maria Foster: A poet, a writer, and a full-time RVer. Loves fishing with her four-legged friend.
Maintaining a fish tank can be fun and exciting. You can add wood, plants, rocks, and stones to it — even fossils. The possibilities are endless!
Before you dash to the nearest beach to hunt for fossils, take a breath. There are important things to consider before decorating your fish tank with them. Your fish tank is a self-contained ecosystem on its own that is host to a variety of organisms and microorganisms such as algae, bacteria, and tardigrades. It’s therefore important to consider how anything you add to it might affect the delicate balance inside your aquarium. In this article, we’ll guide you through everything you need to know and do before adding fossils to your fish tank.
How Are Fossils Created?
Fossils are the preserved remains of plants and animals. When the conditions are just right and an organism doesn’t decay or get eaten, its physical shape and form are left behind in sediment. The oldest fossil discovered is estimated to be 3.5 billion years old. These organisms become fossils by:
- Authigenic preservation. Molds or casts of destroyed or dissolved organisms.
- Carbonization/coalification. Carbon remains in the specimen where other elements are removed.
- Permineralization/petrification. Rock-like minerals slowly slip into the original organic tissues replacing them with calcite, pyrite, and silica thereby forming a rock-like fossil, which can be both hard and soft.
- Recrystallization. The hard parts of an organism revert to more stable minerals. Alternatively, small crystals turn into larger ones.
- Replacement. The hard parts of an organism are replaced by minerals like calcite, iron, pyrite, and silica.
- Unaltered preservation. Parts of plants and insects are trapped in the sap of a tree.
Are Fossils Safe for Fish Tanks?
Fossils can have mineral or metal content such as calcium which can potentially harm your fish. There are tests that you can do at home to determine if a fossil is safe for your aquarium. An even better option is to have a geologist analyze the content of your fossil.
How can a fossil affect your fish tank? The carbonate content in fossils can negatively drastically affect your aquarium’s pH level and the alkalinity of the water so you should never add a fossil without inspecting it first. Likewise, aquarium water can completely dissolve some rocks and fossils, destroying your valuable specimen.
Rocks To Avoid
You might have noticed a wealth of fossils sold online and in pet shops. However, just because they’re being sold for aquariums doesn’t mean they’re right for the one you have. In general, you should steer clear of pointed and sharp-edged rocks since they can injure your fish.
Additionally, saltwater and freshwater aquariums will have different rocks in them. What’s safe for one may not be good for another because aquarium rocks can affect the water hardness and pH levels of your fish tank. You should also consider the individual needs of the species living inside it. If you have a saltwater tank, the following rocks and decorations should work fine:
- Crushed coral
- Dolomite
- Geodes
- Limestone
- Marble
- Shells
If you have a freshwater aquarium, consider the following rocks:
- Lava rocks
- Quartzite
- Rainbow rocks
- Petrified wood
- Onyx
- Texas holey rocks
- Sandstone
- Granite
Even if a rock is listed safe for your type of aquarium, there’s no telling if it might hold minerals or fragments that are unsafe for your fish tank. Therefore, it’s always best to run any rock or fossil you want to add through a test before adding it.
How to Determine the Safety Quotient of a Fossil
Step 1
Test the hardness of the rock with a steel knife. If the fossil is harder than the steel, it’s safe but if it’s soft and you’re able to make etches on it or small pieces come off, proceed with the rest of the steps to determine if it’s safe to add.
Step 2
To check the safety quotient of a rock that didn’t pass the strength test outlined in the first step, check for carbonated materials within the rock by checking its pH level. Here’s how:
Method 1
Since vinegar erodes calcium carbonate, you can use vinegar to detect carbonates’ presence in fossils. Pour a small amount of warm vinegar on the fossil. Hold it close to your ear. If it fizzes, it has carbonates in it.
However, vinegar is a weak acid so it won’t always produce that audible fizz. With a magnifying glass, look for fizzing and bubbles on the surface where you placed the vinegar.
Method 2
Based on the same principle, you can also use muriatic acid for testing. Though we outline the instructions here, it shouldn’t be the first course of action especially for minors and individuals with limited experience handling industrial chemicals.
Vinegar works just as well without the risk of blindness, skin burns, and harming your respiratory system. If you must use this method, always use the prescribed safety gear and exercise utmost caution.
Method 3
You can also test the fossil by immersing it in a clear glass container filled with tap water for a couple of weeks. Check the pH level of the water before and after. If you don’t have access to a pH meter, observe the fossil for signs of dissolution or decomposition.
A small change in the pH levels shouldn’t concern you but if the pH level drastically changes, avoid putting it in the fish tank as it can endanger your fish’s health causing shock and even death.
If your fossil has mineral streaks such as red or green rust, don’t bother to test it, it’s not a good candidate.
Are Carbonates Good for Your Fish Tank?
Water hardness refers to the amount of dissolved minerals in water and is a vital parameter when you have a freshwater aquarium. One of the things you need to keep an eye on is the carbonate level in your fish tank. Your aquarium’s carbonate level is important because it contributes to general water hardness and can be used to boost alkalinity (the water’s ability to resist changes in pH levels). How? Carbonate binds to acids when they appear which has a neutralizing effect.
In the right amounts, calcium carbonate is useful for fish to build stronger bones, regulate metabolism and their ion exchange. You therefore need to maintain certain carbonate levels to ensure the health, growth, and longevity of your fish. When the carbonate hardness dips too low, it can cause your fish tank’s pH levels to fluctuate drastically which can harm and even kill your fish.
While water hardness ranges from soft (0 to 50 ppm) to very hard (200 to 400 ppm), a hardness of 60 ppm and above is generally good for fish. Pay close attention to the carbonate hardness levels that the life in your aquarium needs to thrive.
How pH levels work
Your aquarium’s pH levels determine the acidity or basicity of the water. It uses a logarithmic scale that considers a pH level of seven neutral. Anything below seven is categorized as acidic while water above seven is classified as basic or alkaline.
Why is this an important consideration for your fish tank? The pH level in your aquarium is important because sudden changes to it (even if minimal) can stress your fish and affect their well-being.
To make pH levels work for you, identify the pH range that is acceptable for the type of aquatic life you’re taking care of and make sure that the pH level doesn’t change by more than 0.3 units per day. Any more will cause stress to your fish.
Most freshwater tropical fish will thrive between 6.8 and 7.6 pH. Keep in mind that your aquarium’s pH levels will decrease over time as a result of the breakdown of organic material. One of the best ways to deal with this is by replacing some of the water periodically.
When the amount of carbonate goes up, your water’s pH level rises too. If you have saltwater fish in your tank, this shouldn’t be a problem. However, the water hardness required by guppies, malees, and goldfish will be different from what marine fish or African cichlids need so make sure to always take the kind of fish you have into account.
If the tank is big and the fossil is significantly smaller, it should pose a lower health risk to your fish no matter what minerals it contains. You only need to regularly change the water in the tank to make it more habitable. There are certain chemicals, however, that are deadly to certain fish and many invertebrates. Copper is one such example. When placed in a fish tank in even small amounts, it can wipe out all the life in your aquarium that isn’t a fish. You need to be careful because copper is found in many materials such as azurite, malachite, and turquoise.
Calcium Carbonate and Your Fish Tank
One thing you need to always check for is the possible presence of calcium carbonate (CaCO3). On their own, calcium, carbon, and oxygen in small to moderate quantities aren’t likely to do any harm to the life in your fish tank. However, the chemical compound calcium carbonate dissolves quickly in freshwater and could potentially leave behind residue that can clog your filters. This is why rocks with high calcium carbonate content should never be put in your fish tank no matter how pretty they look. A good example is shale which can contain harmful levels of calcium carbonate.
While fish need a healthy amount of calcium, fossils with high calcium content can easily add too much calcium to your aquarium and cause stress to the fish living in it.
You’ll notice if your fish are stressed if they become lethargic, start swimming erratically, or don’t grow as fast. Too much calcium in your fish tank can even cause your fish to die.
How Much Calcium Do Fish Tanks Need?
If you have corals, coralline algae, and invertebrates in your fish tank, you’ll need to ensure that your tank has about 400 to 420 parts per million (ppm) of dissolved calcium. There are a number of ways to add calcium to your aquarium. Some of the preferred methods include adding eggshells, liquid additives, corals, and cuttlebones.
Where Can You Collect Fossils?
You can collect fossils from anywhere as long as they aren’t near an industrial area. Industrial areas can add harmful chemicals to fossils. While they may not be immediately fatal for your fish, their carcinogenic and harmful effects will lead to their deterioration.
Additionally, you should also make sure you’re not picking up rocks and fossils from an area where it is illegal to do so.
Fossil Care Instructions
Once you’ve determined that a fossil is safe, you should clean it by placing it under running water and scrubbing it with a brush to remove dirt and dust. If your fossil is heavily soiled, you can soak it in a bleach and water solution. Alternatively, you can also boil the fossil for 10 to 20 minutes to kill any unwanted bacteria and parasites. Rocks can stay hot for a long time so make sure to give them sufficient time to cool before handling them.
Between the two methods, boiling your fossil in water is the better alternative since bleach can leak into a rock’s pores and contaminate your fish tank later. Because of this, use bleach as a last resort and only for plastic and glass aquariums.
The Takeaway: Make Sure Your Fossils Are Safe for Your Fish
Fossils are a great way to make your aquarium more beautiful. They’re also great objects that your fish can interact with. However, you’ll want to make sure that the fossils you put in benefit your aquarium without unintentionally harming the life inside it.
By following the instructions outlined here, you can confidently and safely decorate your fish tank with fossils.