Types Of Substrate
The main question for the majority of tanks is usually sand or gravel? There isn’t generally a rule on what you should have but think about the fish in your tank. If they are natural burrowers, sand will be easier for them to get into, especially if they are smaller. Gravel and stone could also be a bit sharp for them.
Sand also makes for an increased surface area, in turn allowing for improved anaerobic activity. Gravel, however, comes in the most varieties, options and colours if you really have a look in mind. It is also often easier to keep clean too, especially if you will be using a vacuum.
Other options include crushed coral gravel which can raise the pH levels of your water tank, especially handy when your fish prefer more alkaline levels. It dissolves over time, so will need replacing.
Marbles can be found in some tanks with fish which breed regularly, as it can stop the adults eating the eggs due to lack of access when they fall. Large stones are also frequently used to keep plants safe and in place.
Then there is a soil-like substrate, which is great for planted aquariums. It often comes in little balls as something as fine as the soil would obviously play havoc on water balance. If it is in a tub, you will need to empty the tank before placing and allow the water to settle for a few days.
There is sometimes no reason why you can’t layer different forms, although exceptions to this rule do occur with speciality materials. If you have live plants, using laterite or vermiculite soil-base can help with nutrients, and can sometimes be topped with gravel for an aesthetic look.
In general, most gravel and sand can be used in saltwater or freshwater tanks. But there may be variations which can only be used in tropical or cold water as the salt and pH levels of a marine tank could be detrimental, and likewise, the hotter temperature in some tropical may make some only good for coldwater.
Check before you purchase your chosen substrate, but remember that if you are set on a white stone for your marine tank, there will be a form out there or in aquatic shops.
You can generally purchase gravel in all sizes. How much you need depends on how large your tank is.
If you want to get really technical, multiply the length of the tank by the width. Divide that answer by 10, and convert into kilograms by dividing by 2.2. A 22 x 20-inch tank = 440. Divided by 10 = 44. Divided by 2.2 = 20kg.
Any spare gravel can generally be kept for situations in which some needs to be replaced/changed or can be used as a decorative element for plants and pots.