what should i use sand or crushed coral what is better and why please
My daughter keeps saltwater and prefers the aragonite sand. Crushed coral has larger pieces, and too much food and dirt gets trapped between the pieces. She also has some bottom fish - gobies - and some burrowing animals, and the sand is easier for them to get into and through so the can keep it better aerated. The sand can come in different colors like gray and pink in addition to the white according to where the sand was collected. The colors give an interesting affect to the bottom. Maybe the other colors might have an affect on how much light is reflected and keep the algae down too, but this is only a guess. Crushed coral only comes in white. Either one helps to keep your pH stable, but the sand has smaller pieces, so there's more surface area, and it can dissolve faster. I guess that can be both good and bad. It would release more calcium and buffer the water better, but the larger pieces would last longer. The bigger pieces would let more oxygen circulate through the bottom for the animals that burrow. I guess this is really something you would need to decide based on what you have in your tank and your water chemistry. But I know it's the sand she prefers.
Either is fine, it all depends on your preferences. I have live sand in my tank, most people use live sand just because it has some helpful bacteria in it, which helps out with the biological filter. Live sand does about the same thing as live rock both act as a biological filter, which is important in the breakdown of ammonia and nitrates. Just make sure which ever you choose that you DO cycle the tanks completely. Live sand helps out loads with the cycling of the tank too. So that's a plus with live sand.
Um. As you noted, each has pros and cons, so it really comes down to personal preference. Most people go with sand-- either oolitic, dolomite, or coral-- simply because it looks better suited to a marine tank. However, these also provide you with many of the benefits of coarser coral gravel. Nearly all marine substrates will slowly (VERY slowly) dissolve, releasing hardening constituents (calcium/magnesium carbonate/bicarbonate), which helps to stabilize the pH. With sand, the finer particles allow anaerobic areas to develop, which can be good or bad. These anaerobic patches can be home to denitrifying bacteria that convert nitrate (from fish waste) to harmless nitrogen gas, or if it's a dirty (containing organic matter) substrate, toxic hydrogen sulfide gas. As long as you don't have food or poop collecting under the sand, there is little risk of the latter. With larger grains, you won't get this advantage (or disadvantage). Sand can be harder to clean if you're not used to it, but when you get the hang of it, you'll find gravels an awful substrate (larger substrates hide the waste, allowing it to rot). Sand is also easier on digging animals (fish, snails, etc.). Really, I'd go with sand. the benefits greatly outway the downsides. EDIT: Larger particles PREVENT burrowing, as they are more difficult to move and likely sharper than small grains of sand. Also, as the animals burrow through the sand, they aerate it themselves. Any sand or rock in a tank will become live over time, as their surfaces are colonized by the same bacteria you'd find on storebought live sand.
