Live Rock – How Much Do I Need?

Live rock is so called because it bears some of the tougher life forms that have survived the processes between the wild and the dealer’s sale tanks. In addition it harbours beneficial bacteria that are able to deal with ammonia, nitrite and [tag-self]nitrate[/tag-self].

All marine aquarists can use [tag-self]live rock[/tag-self]. It doesn’t matter if it is a seahorse, fish only or reef aquarium. Live rock of good quality will be beneficial and decorative.

Live rock is expensive, which is understandable, as it is transported by air. Therefore aquarists should consider buying different grades: base rock, which doesn’t show much on its surface and is suitable for the reef base, and premium rock which can be used to cover the surface of the construction. This reduces the cost up to a point.

Once the aquarist has reached the live rock purchase stage, how much should be bought? In a [tag-tec]reef tank[/tag-tec] there is obviously going to be a lot, and the aquarist knows the extent of the reef that is to be constructed. What of a fish only or seahorse tank?

The usual guideline is to use 1½ lbs for each gallon of seawater in the whole system. This is fine – but there are different types of live rock, some quite heavy and some quite light. So what to do?

In the reef system, as already said, the aquarist knows the extent of the intended captive reef. Therefore it is simple, as enough rock will be needed for that construction. Captive reefs are usually 1/2 to 2/3 of the display tank volume. As the reef system holds a smaller fish load to protect water quality, this amount of live rock should be enough. Corals present a very small bio load. Many if not most reef systems employ a sump and deep sand bed so the filtration is more than likely to be adequate. A decent protein skimmer is necessary.

The seahorse tank is similar. Though a reef is not to be constructed, enough live rock to construct a decent decorative pile or two should be purchased. The bio load on these tanks is usually low, as seahorses are not compatible with fish (except pipefish), and, provided routine water changes are done, very often a protein skimmer is not used, though a protein skimmer can be fitted. Seahorse tanks are usually quite small and water changes are not a problem. In addition, Caulerpa macro algae is often grown in the display tank, and this will assist with water quality and make the seahorses feel more at home.

The fish only tank needs caution. This is because these systems are likely to carry a higher bio load, in other words more fish can be kept than in a reef system. The aquarist is not going to keep a reef tank, and may decide to only purchase a little live rock. If this is the case, then additional bio-filtration must be employed, even if this is a canister filter filled with appropriate media. With live rock as the main filtration, the aquarist will need to use a substantial amount, approaching a reef system. In addition, a sump with a DSB would be a great help. An efficient protein skimmer is a must.

Once any of these types of system are set up with live rock, the aquarist must monitor the water parameters for ammonia, nitrite and nitrate, particularly in the early months (this is in addition to the other parameters that are monitored with a reef system). Bio-filtration needs to settle and adapt to the load it has to deal with, so stocking needs to be done gradually with patience.

Setting up a marine aquarium is not the cheapest of activities, and in the future the system is going to hold life. It makes sense therefore not to cut corners with an absolutely necessary part of the system, the life support filtration.

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