Can saltwater tanks just live on a heater and normal filter?
Speaking hypothetically, with frequent enough partial water changes, almost anything is possible. Realistically, it’s a bit more complicated. Back in the 80s, wet/dry filters were all the rage in the saltwater aquarium hobby and were considered an essential piece of hardware for anybody who wanted to keep corals alive. However, they led to nitrate spikes and corresponding diatom blooms. Some simple soft corals were kept alive through frequrent water changes; colt corals, which consume diatoms, did particularly well in some tanks. However, the stony corals were never truly kept with long-term success and nitrate production was a constant problem. In the late 80s/early 90s, the Berlin Aquarium Society began experimenting with live rock and keeping a protein skimmer. This had much more success (although nobody really understood the full implications at first). Nowadays, the common method advocated is similar to the Berlin method, but differs in that substrate is frequently employed (unlik