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Live Rock

When's the proper time to put in live rock for the aquarium to cycle?

By J. Charles Delbeek

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Q. I have recently re-setup a saltwater tank after 18 years of being away from the hobby. Boy, have I been away a long time! Anyway, I thought that putting the old reliable undergravel filter in with powerheads was good, and I purchased a canister filter for mechanical filtration.

After a few weeks of just damselfish I put in a yellow tang and a banded shrimp. I was having to do 50-percent water changes every two weeks to keep my nitrate levels down below 30 parts per million. Since then I have read a lot (Thiel, Sprung, Moe) and am convinced further, after discussing the problem with a local tropical dealer, that the problem is the undergravel filter, which I am in the process of tearing out over the next month. I also installed a wet/dry trickle filter to do biofiltering while the undergravel is being taken out.

When can I start to put in live rock to start a reef tank? Do the nitrate levels have to be zero? What test kits do I need? Are all the kits I see really necessary — silicate, strontium, magnesium, iron, iodide, KH, calcium, phosphate, dissolved oxygen — or can you get by with just some of them?

A. You have discovered a new approach to setting up a reef tank — no live rock! I am not sure what your retailer suggested to you, but replacing your undergravel filter with a trickle filter is not going to help you if your goal is to reduce the nitrate levels in your tank. Given the setup you now have, the nitrates will only continue to climb because the trickle filter is a very effective nitrifying machine!

You could cycle the tank with the trickle filter and then add the live rock — this is not a problem and will work. I cannot be sure whether you intended to do this or not because one would not have included any fish or inverts until the live rock had been added and the tank was checked to make sure it had not cycled again. The live rock should reduce the nitrate levels over time.

A much better way would have been to cycle the trickle filter separately by running it isolated from the tank so that it recirculates by itself. This is done by directing the outflow of the sump back into the top of the trickle filter. You would then add a seed culture of bacteria from another tank or a commercial preparation, and then add an inorganic source of ammonia, such as ammonium chloride. There are several such solutions on the market. Once the filter had cycled you would discard the filter water (eliminating any accumulated nitrates) and refill with new seawater. You would then hook this filter up to your tank containing the live rock, and thus you have a conditioned filter ready without any nitrates added to the tank.

This is the way I set up my very first reef tank in the 80s, but it is not what I would do now. I would not use a trickle filter and would instead invest in a well-designed, effective protein skimmer. I strongly urge you to buy this piece of equipment. The protein skimmer will remove many of the compounds that will eventually contribute to nitrates in the tank, while the live rock will provide more than enough biological nitrification and denitrification.

Finally, some quick answers to your last questions. Your nitrate levels do not have to be zero — below 40 parts per million will yield good results, but lower is better. You should at least have ammonia and nitrate test kits. You should also purchase calcium and alkalinity kits.

Although a pH kit is also a necessity, it is much more economical to purchase a pH meter because you will want to monitor this parameter frequently, and constantly buying test kit refills adds up over time. A pH meter will allow you to better understand the changes in your system and monitor the additions of solutions, such as calcium hydroxide (kalkwasser). A phosphate kit may also be of use if you encounter algae problems.

Welcome back to the hobby. You will only get more and more confused as you go on, but the rewards are worth it!

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