Adding new decorations to a tank:
Usually if they are store bought and specifically made for aquariums, all that is needed is to rinse them well and preferably let them soak in used tank water or dechlorinated water for a few hours to a day, this also applies to new gravel. This will allow any odours the décor has to dissipate and also lets you check to see if the décor releases any dye into the water. If it does, you may need to boil or soak it for a few days until no more dye is released or not use it at all.
Cleaning existing décor:
It should be pointed out that it isn’t a good idea to clean the entire decor in a tank all at the same time, as this will remove some of the beneficial bacteria.
When cleaning aquarium décor, whether it be artificial plants or rocks etc. often just rinsing in used tank water, using a toothbrush (used only for this purpose) or something similar will do the trick to remove slime or algae.
If the algae still doesn’t come off then you can use boiling water and soak the décor for 20 mins or so, which should kill the algae making it easy to brush off & then rinse in dechlorinated water.
using a diluted bleach solution (5% bleach – 95% water), you can either dip the décor in the solution, remove and scrub to see if the algae comes off, if not, you may need to soak it for 5 mins, but keep in mind that soaking it for a long time may cause some discolouration depending on the type of decor. After using bleach, you need to rinse the décor very thoroughly in dechlorinated water using 3 times the necessary amount of water conditioner because bleach is toxic to fish, until all the bleach odour has gone, and then let the décor air dry naturally, preferably in sunlight.
Before adding driftwood to a tank, you need to brush any dirt/dust off it and soak it for a few days, even longer if necessary, to make sure it has become fully saturated with water so that it won’t float and this also releases any tannin, which will discolour the water, to be leeched out. These tannins are not harmful, but can gradually lower the PH level of a tank. Although, some fish that come from the Amazon regions prefer tannin stained water.
To speed up the release of these tannins, you can also boil the driftwood for a couple of hours which will also kill any fungus/algae spores on it. Pre-packaged driftwood hopefully shouldn’t have any spores on it anyway.
Cleaning existing driftwood:
To clean driftwood, I would NOT use a bleach solution because driftwood is too porous and any bleach that was absorbed, even the smallest amount may still remain which could poison the fish.
If using décor not specifically made for aquariums:
If you want to place an object in your tank that hasn’t been made for aquariums or says it is aquarium safe, there are a few things to be considered first:
What is it made out of...?
Will it affect the water chemistry...?
If it is painted, is the paint safe for fish....?
Will it degrade/disintegrate in water....?
Will it release any dyes or toxins that could harm fish...?
Does it have any metal parts.....?
Does it have any tiny parts that the fish might eat that could get stuck in their throat....?
Does it have any sharp parts on it that could injure fish....?
Most ceramic pots or coconut shells are safe for aquariums, but should still be boiled as previously mentioned, particularly if taken from outside, this will sterilise and kill any spores/bacteria that may be on them.
The Vinegar Test:
Many rocks or rock like decor may contain calcium compounds/limestone which will increase the PH/alkalinity/hardness of the water, so a good test to see if they will or not is to add a few drops or a teaspoon of natural white vinegar onto the rock/décor and if it creates a lot of bubbles, fizzes creating a hissing noise or foams up then that means that it will increase levels and shouldn’t be used. Keep in mind that some rocks/structures may bubble slightly if they are porous and this doesn't mean they are unsafe. If you think they are safe, these also should be boiled for 5-20 mins. before adding them to the tank for the same reason as mentioned above.....to kill any spores/bacteria/parasites.
Shells and coral will also raise PH/alkalinity/hardness and it isn’t a good idea to have them in freshwater aquariums.
Disinfecting Rocks and Gravel:
Do not bleach rocks and gravel.
Do not bleach rocks and gravel.
Rocks and gravel must not be soaked in bleach; they will absorb it and upon reuse, most likely lech it out and kill your fish.
Place the gravel and rocks on a tray lined up with aluminum foil and bake at 450F for an hour.
If the gravel is coated, the heat could melt the coating. Test a few rocks and to see the outcome. If the coating melts, then try baking the gravel at only 250F for a longer amount of time.