Reef Ramblings

It has become obvious from the enquiries I’ve been receiving about the ReefrH20 range of products that there is a lot of confusion out there about filtration, particularly when it comes to Nitrate. During my conversations with reefkeepers interested in ReefresH2O it seems that in most cases the cause of elevated levels of Nitrate is down to poor system design. The reasons for this are unclear: poor advice from shops, a poor understanding of filtration requirements on behalf of reefkeepers, a reluctance to spend money on an appropriate amount of live rock, inadequate attention to maintenance, the list goes on …

What is Nitrate?

Put simply, nitrate is a chemical compound formed part way through the Nitrogen Cycle. The Nitrogen Cycle is the descriptive term for the process where the natural action of  various species of bacteria  (biological filtration) break down toxic compounds into ones of lower toxicity gradually rendering the environment safe for fishes and invertebrates. Principally, the Nitrogen Cycle involves converting the toxic chemical compound ammonia into the less toxic compound, nitrite, this in turn is converted to nitrate (not considered toxic although at high levels it may have a deleterious affect on aquarium organisms) and finally nitrate is converted to non-toxic nitrogen gas.

Our concern about nitrate in the reef aquarium is that, along with phosphate, it acts as fertiliser for unwanted or pest algae and that it can also inhibit calcification in corals.

Causes of Nitrate in the Reef Aquarium.

Nitrates can be introduced into the reef aquarium in a number of ways:

• Through the waste processes associated with fishes and other animals.
• In the water used to make up salt water for water changes and through the freshwater used to make up water loss due to evaporation.
• Food used for feeding fishes and invertebrates.
• As a product of decomposition from dead animals and plants.
• In addition, the use of traditional manmade biological filtration can also lead to elevated levels of nitrate.

The more fishes contained in a reef system the greater the potential for higher levels of nitrate, hence greater amounts of liverock should be used to cope with the higher load.

It’s essential that you use pure or nutrient poor water to make up your salt mix and for replacing evaporation losses. Typically the use of water produced by reverse osmosis (RO) will help prevent the addition of nitrate to the aquarium.
Failure to use low nutrient or RO water will lead to an ongoing nitrate problem. It’s far cheaper to buy a RO unit to ensure that you start off with zero nitrate water than it is to continually battle elevated nitrate with nitrate removal media or with expensive (and fiddly) nitrate reactors.

The food you feed your fishes and invertebrates can have a considerable impact of nitrate levels. On the whole, stay away from processed foods, the majority of which contain cheap fillers. Stick with high quality, high protein foods, such as PE Mysis and CyclopEeze Freezerbar, as these are more fully assimilable resulting in less waste being produced.

Remove any dead animal no matter how small and remove any dead or dying plants. Watch out for signs of Caulerpa species macroalage about to go in to sexual reproduction mode and remove it immediately – it’s at this stage that the Caulerpa can breakdown completely releasing all of its stored nutrients into the aquarium.

Manmade biological filtration versus liverock.

The use of traditional forms of manmade biological filtration (MBF) such as  power filters  (external and internal) and trickle towers, although partially facilitating the nitrogen cycle  by processing ammonia to nitrite, then nitrite to nitrate, does not complete the cycle, leaving nitrate as  an end product. Whereas liverock works at its own rate, completing the cycle by breaking nitrate down to nitrogen, it seems to struggle with nitrate produced by MBF. Where a system combines MBF and liverock and has ongoing elevated levels of nitrate often the simple solution to the problem is merely to discontinue MBF. Within a week or so nitrate levels should be seen to reduce.

Liverock.

Apart from the topics previously mentioned a major cause of elevated nitrate is the use of an inadequate amount of liverock to cope with the biological load of the aquarium. The various formulae of “X” kilos of liverock for “Y” litres of water are misleading. These are at the best a rule of thumb recommendation as there are too many variables to allow accurately predicting the quantity of rock required.

There is no such thing as standardised liverock. The filtration capacity of rock varies immensely depending on where it has originated and on its composition.

Some liverock may not have been shipped in live, consequently its time in the dealer’s rock vat will have only allowed for limited inoculation; if all the rock that’s gone through vat has been in a similar condition it may take some time in your tank before it makes any significant contribution to your water quality.

Prescribing quantity of rock by the volume of water does not take into account the actual biological load produced by the inhabitants of the aquarium. For a lightly loaded tank this may be adequate but for a more heavily stocked one it will prove insufficient.

How to Reduce Elevated Levels of Nitrate.

• Use RO water for all water changes and for evaporation top up.
• Don’t overstock.
• Feed high quality, high protein food such as PE Mysis, CyclopEeze FreezerBar
• Don’t overfeed – restrict to the amount of food that is seen to be eaten in 2 – 3 minutes, feeding 2 – 3 times daily.
• Don’t restrict food with the aim of reducing nitrate to the detriment of the health of your fishes and invertebrates
• Perform regular water changes.
• Ensure your tank contains an adequate amount of liverock to cope with the bioload.
• Harvest macroalgae regularly.
• Employ various critters such as small hermit crabs and snails to take care of any uneaten food.
• Encourage micro fauna such as ‘pods by feeding regularly with DT’s phytoplankton
• Add a ReefresH2O block to your sump to increase your reefs filtration capabilities – note: unlike liverock this media is standardised to a known composition and is backed up with figures detailing its capacity for denitrification.
• Clean any mechanical filter media weekly (more frequently if necessary).

Tim Hayes

Midland Reefs

©2009