Not doing water changes means you will be almost guaranteed to lose that angel in time. Regular water changes are a necessary part of fishkeeping, no way around it, unless you have a ton of plants and very few fish - even then, water changes are required occasionally. Without water changes, you get a build-up of nitrates, which at higher levels are toxic. I have a 46 gallon and it takes me approximately 25 minutes to do a water change, just with buckets and a siphon.