A Basic Guide to Keeping Arowanas

1. Keeping good water
1.1 Ph
A ph of between 6 to 7 would be ideal. Monitoring of the ph can be ideally achieved through the use of a ph meter which gives online realtime information on the ph level in the tank. Other ways of monitoring is by the use of a ph pen, or test strips/liquids.
In an established tank, ph is expected to drop over time, therefore buffer is necessary to ensure that ph do not drop drastically and go too low. A drastic drop in ph causes stress to the fishes. Too low a drop in ph can kill off nitrifying bacteria.
Sodium Bicarbonate can be used as a buffer to and keep ph it at the levels desired. A popular brand is Arm & Hammer pure baking soda which can be obtained from supermarts.
An alternative is coral chip/oyster shell/see ham, but the downside of using such is the raising of gh. One school of thought (with origins from Koi management believes that high gh in an arowana tank lead to chipped scales).

1.2 Ammonia and Nitrite free environment
Both ammonia and nitrite are poisonous to arowanas. To ensure that the tank is free of both, one needs to have a a good filtration system. Nitrifying bacteria can clean the tank of both ammonia and nitrite. These beneficial bacteria agents (Nitrosonomas and Nitrospiria) require a conducive environment to perform it's function. As they are aerobic bacteria, lots of oxygen is necessary, secondly it is ideal to provide places for them to cling on to, that is raise the surface area to increase the colony of nitrifying bacteria. Many commercial products are available to assist in this objective.

Any new arowana hobbyist contemplating on starting a tank is advised to take heed of the basic requirements.

For nitrifying bacteria to establish themselves fully, the following is required:

1. The correct ph level, ideal is at 6 to 7
2. At least one month of cycling a new tank. Tank cycling is equivalent to seeding the the filters with nitrifying bacteria. In order to achieve this objective, ammonia must be introduced into the tank and this can be in the form of adding fishes that are constantly feeding and producing ammonia. Another way is to add ammonia without live fish, or what is known as fishless cycling.

Fishless cycling is an ideal way of establishing nitrifying bacteria without the use of live resources, but there are requirements as well. The downside of introducing frozen prawn into the tank is the added risk of contaminating the tank with undesirable bacteria that could pose a hazard to the arowanas when introduced. Decomposition of the frozen prawn begins immediately when introduced into the tank. Removal at regular intervals is necessary, the smell of rotting flesh is already too late. This is a topic to be best discussed after proper studies and experimentation prove it to be completely safe, but meanwhile due to the variability, this is not recommended for arowana keepers.

What Pump should I use?

Fishes produce waste both in the form of ammonia and physical excrement (poo), and this increases with feeding and addition of more fishes. As an arowana grows, the waste produced increases. Poo needs to be physically removed, it gets trapped in filter wool in a sump and ohf and if the filter wool is not washed frequently, the poo finds its way back to the tank in a dissolved state (DOC or Disssolved Organic Compounds), which is unhealthy. The dangers of DOC are in the build up of bacteria which is harmful to fishes. Frequent water changes coupled with cleaning of filter wool can reduce the presence of excrement in the tank. Ammonia (or ammonium in the non harmful state) can be cleared from the tank easily by having a proper filtration system. Besides ensuring there is a large surface area for nitrifying bacteria to cling to, an adequate pump output is necessary to enable the tank to be ammonia free at all times.
Most pumps will show you the output in litres per hour, however this is not the output you should look for. This is because there is a different output at different heights, some pumps are designed to give better output at greater heights. First, what you need to find out is the height. This is the difference between your pump and the height of the tank (the highest point where the return pipe sits). Once you know the height, refer to the corresponding pump output given in the brochure or the box. You find that generally, as the height increases, the pump output declines. You will be very surprised to find that some pumps don't function very well at greater heights and for your purpose you need to find the right pump that will give you the output that will result in a 6 times tank turnover per hour.

An arowana tank requires a high tank turnover rate, a rough guide is as follows.

First, calculate the tank volume in litres. This can be done by entering the tank length, breadth and height in a tank calculator such as this.

Next, multiply the tank volume by 6.

Eg a 6 feet by 2.5 feet X 2.5 feet tank = 1092 litres. Roughly, it is 6000 litres.

Find a pump with an output of 6,000 litres per hour at the height of your tank (you need to look at the curve given in the box or brochure/literature that comes with your pump).

Similary, the same can be applied when looking for an adequate cannister filter or ohf pump. Do know that there is a reduction in turnover rate the longer the piping and the more elbows used. Therefore, it is always better to oversize the pump output than undersize it.

Hobbyists who provide adequate filtration in their arowana tanks usually have the least problems. Inadequate filtration can result in a host of unpleasant surprises ranging from gill curl, HITH (lateral line erosion), chipped scales, and diseases (bacteria infection), etc. Make sure your tank is adequately filtered, and if unsure, check for ammonia and nitrite in the tank, these should be zero in an established tank.

2. Keeping arowanas in a tank filtered by a Sponge filter

Yes, it is possible to do this.
But there are conditions attached. A tank that is filtered by a sponge filter would have ammonium, the effects of long term exposure to ammonium is not documented.
Scooping up of excrement is compulsory as poo left in the tank form breeding grounds for harmful bacteria.
Water change would have to be carefully done in order to avoid a ph spike. This is better managed by having water stored and treated to bring the ph down to the same level as in the tank. The stored water can be treated by adding Ketapang leaves, filtering through peat moss, or even adding sodium bisulfate which is available from off the shelf products.
Ph spikes can leave the arowana with damaged gills or in the worse case scenario, death through ammonia poisoning.
Such tank setups can be an alternative to the sump, Ohf, external cannisters provided one has a lot of time to do the water changes, scoop the poo, and manage the keeping of water stored.
Most hobbyists are busy people, and therefore, sponge filtered tanks are not for the majority of us hobbyists but rather for those who have a lot of spare time on hand.

Keeping plants such as nanas in the tank would help to remove the ammonium and nitrate. It is an excellent idea and works well with a tanning regiment for Reds.


The target audience for this thread is new hobbyists, I will update this thread momentarily, to introduce topics that will be of assistance to new aro owners, or prospective ones.

The contents have been revised on 16th Jan 2011 to incorporate "head loss" when selecting a pump suitable for an arowana tank.