I am a complete beginner.

I am looking to buy a Tank about 20x20. How many fish could I put in a Tank of that size, and do I need to put any live rock or coral in to it? If I can, what would the best coral be for me to look after? What do I need to begin (everything that I would need, from setting up the Tank, to filters etc, etc)?

Even though I'm certainly not one of the local "experts", I may be able to help out a bit. The number of fish depends on about a million other criteria, apart from size. In a fish only system, with no protein skimmer, and "regular" filtration, you're probably looking at 3 or 4 small Damsel type fish (Damsels are great- you pretty much need to hit them with a stick to kill them).  You can up this number by using a protein skimmer, trickle filter (warning- flames ahead), and especially a sump in increase your volume of water. As everyone in this forum will tell you, get the biggest possible tank you can afford. As for corals, some of the hardier, less fussy types like Mushrooms and Leather Corals can survive in a plain old tank, but even these guys, and certainly the fancier ones, need a huge amount of light- 6 or more watts per gallon, minimum.

I strongly suggest, before you get started, either buy a good book (M. Paletta has a good one out) or cruise the net for all the info you can get your hands on. And find a Local Fish Store (LFS) that you can trust- this is pretty much invaluable.

From: Hennie Landman

Welcome to the hobby - I trust you have a large wallet :)

I agree with CK, you should read as much as you can, surf as wide as possible, and THINK. Remember that all shops are in the game to make money. Generally, you will find that advice given by someone with a potential financial gain in the matter will be biased towards the most expensive, least useful items.

Joining this Forum was a smart move - here you will get advice, sometimes quite conflicting, but given without financial motivation. We're in it for love (or maybe because we're slightly mad!). Spend a week or two just surfing or reading - just make sure that the books and/or articles you are reading are less than 2-3 years old. Then, think about what type of aquarium you would like to have "eventually".

Plan for the ultimate you want in the beginning, then buy only that which you need at any particular point of development - it will work out much cheaper this way, and you will enjoy the hobby more..... As an example: If you want to eventually keep SPS corals, you will need strong lights, and very good water quality. So, start off with the right filtration, and buy a light, which you can use later when you "upgrade" to SPS.

From: SV

I'd like to add to HL's advice to plan ahead.  Nothing stinks worse than buying some product that you think will be OK, only to learn in three months that you really wish you had a much nicer model.  (I am thinking of "cheap" lights vs. metal halide or PC lights, and crappy skimmers vs. one of those Berlin models, small aquarium vs. large).

It makes the initial cash outlay MUCH higher, but in the long run you, and your fish, will be happier.

From: Hennie Landman

As a relative newcomer myself, I know just how confusing this all can be. Could I start my advice by first cautioning about the petshops, live fish shops, or whatever you call them. Remember that they are there to sell things to you, things that might not be needed. There are some very reputable shops, but even they must make a living, so BUYER BEWARE! Now for some of that advice you asked for.

You should firstly decide on what type of environment (or should we call it set-up?) you want. A fish only tank is easier to keep, as fishes can withstand a greater degree of pollution and water quality fluctuations. A "reef" tank though slightly more difficult to keep, is much more interesting, and in my humble opinion, gives one a greater sense of achievement and satisfaction. Many people start off with a FO (fish only), only to upgrade to a reef tank later. This invariably results in some equipment having being replaced, because they did not buy "Reef quality" originally. So, I would like to suggest that you buy your equipment with a reef tank in mind, even though you may initially plan to keep only fish.

Now for some specifics:

1. leave the Biowheel, get a sump (a small tank, 10 - 20 gal. would suffice) and the BEST quality skimmer you can afford - this will be your primary filtration unit, so don't skimp on it.
2. Unless you plan on having a very high bio-load (of fish), you don't need a Wet/Dry. However, having said that, I do use one. Just glue 4 panes of glass together to form a tower in your sump, and fill it with an appropriate media. Plastic hair curlers work just as well as plastic bio balls. A porous ceramic media, such as Hagen Bio Max, or similar, works a lot better. Small (40mm - 80mm) live rock reject pieces work even better.
3. Put a thick (3"-4") layer of appropriate sand (coral sand is the best, however I've used local sea sand, and it also works well) in your tank, and as much Live Rock (LR) as you can afford. You don't have to do this all in one go, but try for at least 10% of the tank volume to start with.
4. Two smaller heaters are always better than one large one - if one fails on, it won't boil your tank, and if one fails off, the other will still prevent it from going disastrously cold in one night.
5. Don't use Damsels to cycle - They are very aggressive, and hard to catch when you eventually decide to replace them. The LR should be enough, but you can add one or two frozen shrimps (the human food kind). This will cause sufficient decay to start your bacteria growing.
6. Be careful with using unfiltered tap water. Depending where you live, it could contain pollutants, such as Phosphate and silica, and poisonous metal salts such as copper. Preferably use RO (reverse osmosis) or de-ionised water. If this is a problem, use a household water filter jug, such as Brita. On your tank, you will have to replace the filter canisters a few times, though. If the water is OK, then by all means use a hose pipe - just make sure you shut it off in time :)

I hope this helps, and did not put you off marines. If you have any more questions, please do not hesitate to ask - there are many people on these forums only to happy to help. Lastly, can I suggest you get a good book on the subject, and visit some other online forums as well.