FAQ

I have come across and answered questions about keeping Arowanas in Planted Tanks in various online communities. Most times the questions are variations of the same concerns. Here I will attempt to consolidate these FAQs. Before reading further, please understand that at the time of this writing, I have personally only ever kept one Arowana Planted Tank and one being set up. My answers below are mostly based on my experience with that past tank and the upcoming tank. I may also write about what I have seen, read or heard about other people’s Arowanas in Planted Tanks. In the latter case, I will try my best to make sure I indicate so. This FAQ is a work in-progress at the moment. I am also happy to take questions, so feel free to use the Ask me a Question form below.

Will the arowana eat its tank mates?

In a simple sentence: Yes, if they fit in its mouth.

Do not put any small fishes in the same tank that you are not prepared to lose. The arowana is a predatory fish after all. However, in my experience, it is a rare occurrence. My current arowana has taught me that it differs from fish to fish. I have never seen my previous arowana actively hunt down its tank mates. However, my current one, when it is active, will try to eat the SAEs. The SAEs have so far been able to stay away or escape.

  1. A lush planted tank provides lots of cover and the prey are smart enough to stay hidden when the arowana is active.
  2. The same smart prey knows how to stay away from the jaws of death. I had Siamese Algae Eaters and Tiger Barbs in the tank with my previous arowana and sometimes they still dare to swim in the open, but only behind the arowana. Once it turns around, they go back hiding in the plants. My current batch of SAEs stay near or under cover mostly, they only swim in open water when they smell the arowana’s pellets, to try a grab any crumbs or missed pellets.
  3. Most predators will not expend unnecessary energy to catch its food. If your arowana gets fed regularly and fed well enough each time, it should wait for the easy food and not bother to chase difficult food. However,my current arowana is proving me wrong.

Tips

  • If possible, get an arowana that was trained from young to eat non-live food. Like pellets and market prawns.
  • Keep middle and bottom swimmers. Arowanas have upturned mouths which are designed for prey swimming near or on the surface, and hanging off plants above water. An aggressive arowana may still try to eat the such tank mates but is not well equipped to do so.
  • Keep fishes that are agile and fast.
  • Do not keep too many other fishes.
  • Do not keep any fish or other tank makes that have spikes, thorns, poison, etc. E.g. Otocinclus and snails with spiky shells (I have seen my first arowana chomping on tiny snails a couple or times).

Large Fishes

Fish that are too large to be eaten are safe from the arowana. However, you may want to consider whether your arowana is safe from them. Also, a planted tank needs to maintain comparatively low levels of Ammonium/Ammonia, Nitrites and Nitrates. Having a high fish load would make it difficult to keep the algae away.

Will the arowana damage/destroy the plants?

My first arowana was a juvenile, about 8 inches long, when I introduced it to my planted tank. It adapted well and never tried to purposely remove or destroy the plants. There are many other people who successfully keep arowanas in planted tanks.

My current arowana was also introduced into a fully planted tank as a juvenile. It is mostly living peacefully with the plants.

The main cause of plant damage by my arowanas are when they try to eat a fish that was resting on a large leaf or trying to escape through some plants. My current red, though, has been observed trying to remove some of the taller plants in its way. So far no significant damage caused by either fishes that are obvious.

As far as I know, arowanas do not make “nests” like some species of Cichlids and other fishes, hence will not instinctively try to move your tank contents around. However, I have read a few posts where plants were introduced into the tank of an adult arowana which had been living in the same tank for many years. Those arowanas did not like the intrusion and pretty much destroyed the plants.

My personal take: if you have an older arowana that has been living in the same bare tank for many years, then you will have to test its tolerance with a few cheap plants on wood or in pots first.

Will the arowana hurt itself on the hardscape (rocks and wood)?

Possible, but unlikely, if you scape wisely. Arowanas are large, active and powerful fishes. Aggressive ones may try to chase and eat their tank mates. When frightened, the arowana, like most fishes, may dart away suddenly and in some cases, blindly. Scape so that (1) the hardscape is unlikely to be in the way, and (2) that if they do knock into the hardscape, injury is minimal.

Rocks can be used in the lower part of the scape. Use rocks with smoother surface instead of the very rough ones or ones with sharp knife like edges. Use roundish rocks rather than pointy rocks. For wood, instead of placing them to stick up like branches, place them so that the sharp pointy bits point are buried in the substrate, like exposed roots of trees. Try to keep most of the hard scape below half the tank. Use soft plants with tall long leaves to fill up the upper spaces at the sides or back to balance the scape.

Will the tank mates get stressed out by fear of the arowana?

It depends. I’ve seen a video of a tank with a rock and plant feature in one half of the tank, and a tree like driftwood with attached plants in the other half, on an otherwise flat plain of carpet plants. There was a stressed looking school of Neon or Cardinal tetras swimming to and fro between the rocks and driftwood as the arowana glided from end to end of the tank. On the other hand, in the same video, there were Yamatos and Otocinclus happily grazing among the plants and clinging on the hardscape and glass.

In my own tanks, the small tank mates are constantly alert and cautious, but do not look constantly stressed to me. In my opinion, if you provide ample havens with plants and hardscape where the small fishes can feel safe, they are less likely to be stressed by fear. They know they have places that they can rest safely in and will instinctively balance the risk between safety and feeding.

What algae eaters can be used?

For my new tank:

  • Zebra Nerite Snails – without the spikes on the shell (NS)
  • Bristlenose Pleco (BN)
  • Siamese Algae Eater (SAE)

Word of caution: I’ve never used the first 2 above in my previous tank. I decided on these for my current tank and I’ve yet to see the outcome. I’ll update here when I know more.

SAEs are generally fast and agile. They survived well in my previous tank and only one got eaten because it nibbled on the arowana’s meal and was too slow to get out of the way. My current arowana is far more aggressive and is constantly on the look out for opportunities to eat the SAEs. So far, 2 confirmed eaten and 4 unaccounted for.

My worry with NS is that they climb into my weir and choke up the drain pipe. I’ll be rigging some wire meshes to prevent that from happening, but you never know… nature has a way of getting into anything. I’ve seen my previous arowana try to eat the tiny snails in my tank. You can see it in the video of my arowana. On one other occasion I’ve seen shell fragments spilling out of its mouth as it chomped on something (probably a ramshorn snail). I am wondering whether it would try eat NS. However, I doubt so as the NS shell is a lot tougher and I don’t think the arowana will swallow it whole. On the other hand, I worry it will swallow one and have it stuck in its stomach.

Update: My snails died before the arowana was introduced. So the jury is out on this.

I am planning to get got the Starlight Bristlenose Pleco (L183). These are beautiful fishes and get to about 6 inches only, not too big. There are many other types of BNs and most get to about 8 to 9 inches. Most BNs are nocturnal by nature, so hopefully that and their size (not very small) will keep them safe from the arowana. The concern here is that they will sometimes scrap on the large plant leaves like those on the Red Tiger Lotus or Amazon Sword Plants and leave them with large unsightly holes. I had one in a smaller planted tank and it did not bother the Red Tiger Lotus in the tank. Other fish keepers report otherwise. It would seem it depends on fish to fish.

Update: My Starlights have so far left my lotus leaves alone. The bad news is they started hiding under the plants and wood and stopped cleaning the glass after getting harassed by my arowana. The sort-of good news is the arowana may (this is a guess) have tried to eat one of them and learnt they are too spiky. That said, all my Starlights are all alive and healthy. Many times I have seen the arowana make a beeline for their location after seeing movement and then turn away at the last moment when it gets close. I can only guess it tried before and got a mouthful of spikes and the victim actually survived. Recently, I have seen them venture a short distance away from their wood and plant havens to graze on the sand, and also large partially cleared spots in the film of algae that I get on glass weekly. I am hoping that as they get bigger they will dare to come out to graze on the open areas, including the glass.

Many commonly used algae eaters are small enough to be eaten and many of them, like Otocinclus, have spiky scales. My first arowana manage to catch an Otocinclus affinis and nearly choked on it. Fortunately it was able to cough it out. It learnt never to eat Otocinclus again, and I learnt the risk of using them in the a predator tank. Shrimps never live long in my previous tank, though I never witness them being eaten by my arowana, I have not been able to find the bodies. My conclusion is that despite their skittishness, shrimps still get caught easily by the arowana. My current arowana is so aggressive that I don’t think I should bother.

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