Dear ageber:
Yes, sir, the porous interior of pre-cured live rock houses a considerable population of both aerobic nitrifying bacteria and anaerobic denitrifying bacteria, and this can provide the aquarium with some limited instant biological filtration ability and therefore help accelerate the cycling process. Live sand likewise contains both Nitrobacter and Nitrosomonas nitrifying bacteria, which helps speed up the nitrogen cycle by providing the necessary "seed" bacteria to kickstart the whole cycling process. But the use of live rock and live sand, or pre-aged saltwater, will not eliminate the need to cycle your aquarium entirely. You will still need to provide a source of ammonia to feed the beneficial bacteria and build up a sufficient population of the "good guys" in order to handle all the wastes produced by your seahorses, and you will have to monitor the aquarium closely while it cycles in order to determine when the process is complete.
Besides using live rock on live sand, there are a couple of other things you can do to further accelerate the cycling process. For instance, you can increase the aeration and the temperature in the aquarium while it is cycling. The beneficial nitrifying bacteria (Nitrosomonas and Nitrobacter sp.) that convert ammonia to nitrite and nitrite to nitrate are all aerobic or oxygen-loving microbes, so their population will increase faster if there is a high level of dissolved oxygen in the aquarium. Adding an airstone to provide better surface agitation and promote efficient aeration and oxygenation while your tank cycles should be helpful.
Secondly, I would raise the temperature in your aquarium to around 80°F while it cycles. Bacteria multiply faster at warmer temperatures, so raising the water temperature should help stimulate faster growth of the beneficial nitrifying bacteria as well. (Don’t forget to reduce the aquarium temperature back to normal once it’s finished cycling so that it’s optimal for your seahorses.)
There are a number of different ways to seed the tank with bacteria initially and feed it with ammonia so cycling can proceed. Two popular methods are the fishless cycle, which I recommend, and the use of hardy, inexpensive (i.e., expendable) fish to produce ammonia and cycle the aquarium. Often used for this method are marine damselfish or mollies, which can easily be converted to saltwater. Both are very hardy and generally survive the cycling process, but I find this method to be needlessly hard on the fish and exposing them to the toxic ammonia and nitrite produced during cycling certainly causes them stress. Damselfish are far too aggressive and territorial to leave in the aquarium afterwards as tankmates for seahorses. Mollies are a possibility, but they really look out of place in a saltwater setup.
So all things considered, I recommend cycling your tank without fish, just as Katja suggested. It’s really very easy. To use the fishless cycle, you need to add something else that will increase the ammonia level so the nitrifying bacteria can build up. I like to use a piece of cocktail shrimp (regular uncooked eating shrimp from the grocery store) and leave this in the tank to decay during the whole cycle. The decaying shrimp produces plenty of ammonia to kick-start the cycling process.
After about 3 days after you add the shrimp, you will notice a spike in ammonia levels until the Nitrosomonas bacteria build up enough to break down the ammonia. When that happens, you will notice the ammonia levels rapidly dropping. (If for some reason your ammonia does not hit the top of the charts initially, you may want to add another piece of shrimp.)
The byproduct of ammonia is nitrite, and during this stage of the cycling process, as the ammonia falls, you will have a corresponding increase in nitrites until the population of Nitrobacter bacteria builds up. Nitrite levels will then fall as the Nitrobacter convert the nitrite to nitrate.
It is important to use your test kits every day or two when cycling your tank to monitor the progress of the process. As described above, normally at first you will see a rapid rise in ammonia levels with no detectable nitrite or nitrate. Then, as Nitrosomonas bacteria begin converting ammonia to nitrite, the ammonia levels will fall and nitrite readings will steadily rise. Nitrite levels will peak as the ammonia drops to zero. Next, Nitrobacter will begin converting the nitrite to nitrate, and your nitrite readings will fall as the level of nitrate rises. Finally, after the nitrites also read zero, you are ready to stock your tank. At this point, your ammonia and nitrite levels should both be zero, nitrates will be building up, and algae will usually begin to grow. This will tell you that your biofilter is active and functioning properly, and that you can now safely begin stocking the tank. It generally takes about 3-6 weeks to cycle a tank this way from scratch. But if you’re using live rock and live sand, along with pre-mixed, aged saltwater, you can expect a much faster cycle. Just monitor your tank as suggested above and you’ll know when it is safe to transfer their seahorses to the 90-gallon aquarium.
Best of luck with your aquarium upgrade, ageber!
Happy Trails!
Pete Giwojna
Ocean Rider, Inc. is an Organic Hawaiian-Based Seahorse Aqua-Farm & Aquarium that Follows Strict Good Farming Practices in Raising Seahorses and Other Aquatic Life.
