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Marine or Tropical Fish?

Marine or Tropical

For many people, marine fish are instantly more attractive than their freshwater counterparts, and although both require the same fundamental care there are a number of differences between tropical marine fish and tropical freshwater fish. If you are starting out, or have a limited fish keeping experience, you will need to understand and consider these differences before you make your choice.

Are marines difficult?

One of the most common question asked is whether marine fish are more difficult than tropical fish to keep, but this can be answered in a number of ways! In terms of time involved, marine tanks can take less or more time and maintenance than a freshwater tank depending on the complexity of your setup and the types of livestock you are keeping. A 'fish only' marine tank will require a similar amount of maintenance as any other tank. A marine 'reef' tank, containing a full range of fish and inverts (corals, shrimps etc.) will require a fair bit more care than a freshwater tank.
The 'difficulty' in keeping marines comes in a greater need for an understanding of the environment, as well as learning about extra bits of equipment, understanding a little water chemistry, and being more vigilant with maintenance and water changes. For some fish keepers this is enough to put them off, for others it adds many extra dimensions to enrich their hobby even further. Put simply, you can start a tropical tank and learn as you go with the odd mistake here and there, but take this approach with a marine tank and you are asking for trouble.

What is the big difference between marines and tropicals?

When we keep fish we are actually keeping the water, or the aquarium, rather than the fish. It is the environment that the fish are kept in which is most important, and it must reflect the conditions our fish have evolved over millions of years to live in. This is where the fundamental difference between marines and tropicals lies, and it is the reason why marines require a different approach when we keep them. To understand this a little easier consider the following analogy:
marine and freshwater tropical fishTropical freshwater fish come from a varied range of areas such as pools, lakes, streams and rivers - one thing all these habitats have in common is that they are affected by the surrounding environment. Weather may cause a cooling or warming of the water, the water chemistry may be changed by water runoff from surrounding land, there may be floods or droughts etc. These are all factors tropical freshwater fish have evolved to deal with.
If we now look at our marine fish, which come from tropical reefs, we find they are not affected by these variations in their environment. Whilst weather does bring storms and disruption, the basic environment in terms of chemistry and composition does not change because the oceans are so vast that localised disruptions (such as heavy rain) are very quickly diluted away. In an aquarium environment, tropical freshwater fish are much better placed to cope with chemistry changes and less than ideal conditions than marine fish are. Missing feeds, irregular water changes, high nitrates and minor pollutants, incorrect maintenance etc. are all fairly easy to recover from for most tropical fish, but not for marines.

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