Hi guys I'm converting to marine as u problem know.
I've got a 450 litre tank I was just going to use a hob protein skimmer and live rock is this enough for FOWLR as I've been talking to some guy in fish shop and he said that's not enough said I need a sump or it won't work is this true
No, you could get away with going with a HOB skimmer and the canister filter but generally speaking, with a tank that size it is not the way to go. The way you are looking to setup things you are going to have to do frequent larger water changes to keep up with the nutrients that a low stocked FOWLR tank.
You could start that way but you are going to have to keep your stocking level low. If you keep up in the hobby you are going to want more fish and more filtration. A sump provides room for a conventional skimmer, and other filtration / nutrient export equipment. Generally I have found that spending money on equipment that is not going to cover your long term needs ends up eating up funds you could be putting in to other things. For example if you find that your HOB skimmer is not working well enough you will have to replace it, you would be lucky to get back 1/2 of what you spent on it if you sell it, and then you have to spend the money for the Skimmer you really need and a sump for it. Instead you could go with the sump and a skimmer that will defiantly meet your needs. Then later when you would have been looking at getting a better skimmer you can use the money for other equipment, or more fish.
I am not a fan of canister filters as they require a minimum of weekly maintenance to keep them from turning in to raging nitrate factories. No matter how you use them they will end up acting as a mechanical filter, catching food and waste which will breakdown in the filter. If you are going to have mechanical filtration I find filter socks to be much easier to replace, since you do not have to shut down anything to do it and they can be swapped out in a minute or less. I change mine every 3 days, this prevents nitrate buildup from the food and waste breaking down, and insures it does not get in to my media reactor, keeping it from turning it in to the same nitrate factory a canister filter would be. You could use the canister filter as a media reactor if you have a mechanical filter before it, and that is exactly what I did for a while. I upgraded to a media reactor after a year to make my maintenance easier, so I could run GFO and Carbon with out bags, and so I could monitor the media itself.
Another reason to go with the sump instead of the canister filter is the overflow that brings the water to the sump uses surface skimming, this is important in salt water tanks since they will develop a surface film if it is not drawn off. This film will inhibit good air exchange and looks bad.
There are a lot of other reasons I could give you to go with a sump, but instead let me say this, read the threads and the articles here, plan your tank build, figure out what everything is going to cost you, then decide what you can live with. I would recommend you factor in your plans a good RO/DI filter and a water storage and mixing station. Mixing salt water in 5 gallon buckets and having to carry them around full of water sucks, and probably is the #1 reason people slack off on water changes, which is guaranteed to cause a tank crash.
