first of all, you really need to know about the cycle of tanks before buying a aro.
with smaller fish, that do not produce so much waste its different.
arowanas produce VASTS amount of waste! wow, you wont believ eit. They can digest food in a matter of hours and hungry for more.
mine eat 3 to 4 shrimp a day thtas bigger than its own face. thats in one day!
Firs ti would google the info on Amonia, Nitrite and nitrates.
Then iw ould get test kits
i personally dont check them anymore, i have massive filters, i know they are cycled well and just change water, but occasionally i check to make sure, i just change the water regularly, 30 to 40% every week or twice a week.
i have a fluval fx5 and a over flow also.
you need to ensure your filtration is enough.
the tank size seems ok, it can stay there for abit more. as long as the width of the tnk isnt less than then length of the fish, then i guess its ok.
go to the fish store, and buy some CYCLE or a concentrated bacteria solution. Rea sea makes good ones.
Pour a few capfulls in there daily.
make sure you have plenty of BIO MEDIA in your external filter. Not just filter wool.
Clean the gravel or remove it completely for awhile.
Arowanas are really really messy animals, they crap a whole lot of toxins all the time. so you need a strong ass filters, 1000 litre per hour filter isnt enough sometimes, because thats the output at level on the water line, but their effectiveness is probalby just 200 to 300 litres per hours of actual filtration.
