Seawater Parameter Guidelines

Over and over the importance of seawater quality is emphasized. Seawater quality is the number one requirement for the marine aquarium, be this fish only, coral only or mixed reef. Most corals demand light for health and growth, nevertheless seawater quality is still the number one need.

Guidelines are useful for those who are not experienced in the marine hobby, including those who are setting up an aquarium for the first time as they can help towards purchasing the correct equipment such as pumps. They are also useful for those who feel their aquarium is not as it should be, perhaps fish are not as colourful as expected and corals slow to extend and show polyps. There are several reasons why this could be so but the first place to examine is the seawater.

Even if the seawater was at the correct parameters when first used, as soon as it enters the aquarium where there are life forms it begins to deteriorate. This needs to be counteracted by routine seawater changes of the correct amount and at the correct intervals.

As far as the guidelines are concerned, this is just what they are – guidelines not absolutes. The requirement is quality and stability. The guidelines give a starting point and it is up to the aquarist to carry out tests and know the trends of his/her aquarium. The use of a notebook to jot down the results of various tests is recommended, it takes very little time. The notes will indicate the need for supplementation for example, and at what period and amount. Another example is that notes will indicate the effectiveness of routine seawater changing – is nitrate increasing, stable, or perhaps decreasing? Should the amount of seawater changed be increased etc? Once the aquarist has gained experience then the guidelines can be amended if necessary, but always with caution.

Experienced aquarists could run their aquariums at levels clearly different from the guidelines. This could be for various reasons, such as a low SG (specific gravity) to combat certain fish problems. When any particular action is contemplated, always consider the potential impact it could have on other livestock types in the aquarium before proceeding. Research of livestock requirements is always worthwhile.

General guidelines are given for fish only and reef aquariums.

Temperature: Fish only and reef, between 75 and 80degF. As temperature increases oxygen decreases. It could be best to choose a ‘middle’ temperature of 77degF. Some experienced aquarists use a temperature a little over 80degF as this increases the metabolism of the entire aquarium population – again, caution is required.

SG (Specific Gravity): Fish Only, often from 1.020 to 1.022 though it can be higher (and should be if corals are present). There is some suggestion that certain unwanted parasites that afflict fish fare less well at a lower SG.

                                      Reef: normally 1.024 to 1.026.

pH (Potential of Hydrogen). Fish Only and Reef: between 8.0 and 8.4. A pH of 8.3 is often quoted as the ideal reading, and this is generally so, but other readings are acceptable with stability.

Alkalinity: Fish Only, seldom measured unless pH is a serious problem.

                    Reef, between 8 and 12 dKH.

Ammonia: Fish Only and Reef, nil.

Nitrite: Fish Only and Reef, nil.

Nitrate: Fish Only, below 30ppm but always as low as possible.

                Reef: below 10ppm but always as low as possible.

Phosphate: Fish Only, seldom measured unless algae is a serious problem.

                      Reef, undetectable.

Calcium: Fish Only, seldom measured.

                 Reef, Soft Corals – around 375/400ppm. Hard corals – around 450ppm or a little higher. Calcium also assists other life forms such as snails.

Routine Seawater Changes: Fish Only and Reef, 10% of the net gallonage of the aquarium (including sump if there is one) carried out weekly. Even if parameters remain healthy it is recommended that seawater changes continue, though this could be at a reduced level if applied with caution. Remember that seawater changes ‘freshen’ the aquarium and replace trace elements at least partially.

Seawater Movement: Fish Only, around 10 times the net gallonage of the aquarium (excluding any sump).

                                          Reef, Soft Corals – the same as fish only. Hard Corals, around 20 (or a little more) times the net gallonage of the aquarium (excluding any sump).

The guidelines given do not include items such as Iodine, Strontium and Magnesium which mainly apply to reef systems, particularly those stocked with hard corals. With some of these there is argument over how beneficial they could be. For basic purposes such inclusions generally confuse matters.

If the aquarist maintains basically high quality seawater and applies other necessities correctly, for example lighting and seawater movement the aquarium display should be beautiful. Additional considerations, if any, arise as experience grows and the trends and needs of the aquarium become known.

  1. Really enjoyed this! Well done!

  2. Hello ???. I’m glad it was enjoyable and I hope informative too.

  3. Aloha! I’ve just stopped by to thank you for this interesting entry. Take care!

  4. Hello cialis. Thanks for the thanks!

  5. This article is very useful. Because it’s one thing to tell people you need to monitor your calcium, alkalinity, pH, nitrates, phosphates, etc.. But what good is that if you don’t know what your targets are for each parameter?
    Good article.

  6. Thanks Warren. An important point is that the guidelines are starting or initial reference points, it could be the requirement for one or more of them (ie. the targets) will change and the aquarist needs to adapt to this.

  7. Seriously, I absolutely liked reading your blog post. You have convinced me to subscribe to your blog.

  8. Great and welcome!

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