My SPS growout tank, a 75 gal uniquarium is basically bare bottom on one half of the tank (where the coral rack is) and a thin (1/2"-1") black hawaiian sand and rubble substrate on the other half. More sand than rock rubble. I believe that the rock rubble pieces shouldn't be stacked on top of each other to avoid detrius build up. The rubble in there acts more like an anchor for the sand in the high flow than for actual substrate. Also, I use the rubble as frag bases, and constantly replace the used rubble with new. The few problems that i've run across with the rubble is that it does trap copious amounts of detrius, even with the extremely high flow rates of my SPS system. This is easily maintained by simply gravel vacuuming the sand/rubble every time I do water changes. I also believe that by using the rubble pieces as frag bases, and constantly removing and replaceing them, I also am removing any concentrated toxins that the rubble may have absorbed, not to mention that the substrate gets stirred in the process.
Bieng that there is no large live rock pieces in the tank, I replaced the bio-balls in the built-in trickle filter system with about 25 lbs of live rock rubble as well for biological filtration. This tank has been up and running for 3 years now, and I have found great success with growing and propagating even the most difficult species of SPS corals like the Acropora hyacinthis (table acro) and I like the way it looks
especially with the black sand. The only issues that ive had with this system is Nitrates, due to the trickle filter, even with the rock rubble as the main filtration media. While I would reccommend this method to others who are concious of their husbandry and regular water changes, I would strongly discourage weekend warriors to use rock rubble as a substrate to those who are lax in their maintenance routines. This setup definitely requires more maintenance than the standard sand bed tank, and would prove to be problematic if the regular water changes were not done. One thing that definitely helps with this issue is the use of the services provided by the copius nubers of Nassarius obsoleta and N. illanissa snails which constantly stir the sand by burying themselves and coming out for food. I believe this also adds to the health of my SPS corals by providing an additional food source, mmmm fish poop.
Bieng that there is no large live rock pieces in the tank, I replaced the bio-balls in the built-in trickle filter system with about 25 lbs of live rock rubble as well for biological filtration. This tank has been up and running for 3 years now, and I have found great success with growing and propagating even the most difficult species of SPS corals like the Acropora hyacinthis (table acro) and I like the way it looks
especially with the black sand. The only issues that ive had with this system is Nitrates, due to the trickle filter, even with the rock rubble as the main filtration media. While I would reccommend this method to others who are concious of their husbandry and regular water changes, I would strongly discourage weekend warriors to use rock rubble as a substrate to those who are lax in their maintenance routines. This setup definitely requires more maintenance than the standard sand bed tank, and would prove to be problematic if the regular water changes were not done. One thing that definitely helps with this issue is the use of the services provided by the copius nubers of Nassarius obsoleta and N. illanissa snails which constantly stir the sand by burying themselves and coming out for food. I believe this also adds to the health of my SPS corals by providing an additional food source, mmmm fish poop.
