Custom fish tanks are expensive to set up so you will need to be sure that they remain healthy. You have to be disciplined in the care of your aquarium. This means feeding your fish on time, frequent cleaning sessions, maintenance checks and observation of the fish to make sure all is ok. If you feel that a fish or fishes are unwell you should seek help or you can run the risk of losing your entire collection.
There are several troubles that can be expected and should be ready for. These include:
1) Equipment failure: In the unlikely case your custom fish tanks were to break what would you do with your fish? You should know the answer to this question. Either you've a temporary but suitable alternative home or have an arrangement in place with your nearby dealer. If it's pump that fails you should have an extra one available. Regular checks & maintenance might prevent either of these events happening but you can not be too careful.
2) Electricity outage: if you live in an area at risk of electricity failures you probably already have a backup generator or emergency plan in place. If not you should sort something out specially if your tank relies on the electricity supply to maintain healthy living conditions. If a power outage catches you by surprise use an insulation blanket to cover the tank so that you can aid to preserve the temperature of the fish. You can raise oxygen levels in the tank by using a bicycle pump for five minutes every hour. If you don't have one of these you can try breathing into the tank using a straw. Keep feeding at a minimum during a failure as the filter systems will not work unless they are running on a backup battery.
Custom fish tanks may look great but it may take a bit extra work from time to time.