FO vs FOWLR vs Reef Tanks

A one spot foxface in my tank

I mentioned in my first post that there are different types of saltwater aquariums and in this post we will explore what those types are!

Fish Only

A fish only, or FO, system is just what it sounds like. It’s an aquarium that only has fish! There are no giant rocks or corals in this tank. It might include some sand or other tank decorations but it’s a pretty simple set up. This is by far the easiest system to set up and maintain as all you need is saltwater, a heater and something to move the water around like a filter or powerhead. A light is a great thing to have but the light you pick can be a very cheap light. You only use your light here to view your fish so any simple light fixture would work.

Fish Only With Live Rock

This system, also called FOWLR, does not have corals but it does contain natural reef rock. In order to convert a FO system to a FOWLR system all you have to do is add rock. This can be done at any point so it’s easy to upgrade in the future if you start with a FO tank.

Dry rock. Photo from Amazon

Rock comes in two forms – dead/dry and live. The difference is that dead or dry rock is, of course, totally dry and has no beneficial bacteria on it. Dry rock is cheaper than live rock. It also is great for people who want complete control over what goes into their system as there are no little hitchhikers that can come in on this rock.

Live rock, on the other hand, has already been placed in a saltwater tank and given time to allow it to hold a bunch of beneficial bacteria. These bacteria help with the nitrogen cycle and keep ammonia in check. If you want your tank to cycle faster you can use a little bit of live rock to help seed your tank. This often reduces the tank cycle from a couple months to a few weeks. Live rock can even help bring in new organisms into your tank. Both good and bad pests can make their way into your tank this way and you’ll be surprised at the amount of life that can hide in tiny crevices! We’ll discuss good and bad hitchhikers in another article though.

A tiny orange starfish hitchhikes in on live rock. Photo from Tampa Bay Saltwater

If you’re looking for a single live rock to seed your tank I recommend going to your local fish store, LFS, and buying a rock there. If you want to buy a large order of live rock there are a few places you can turn to. One example is Tampa Bay Saltwater. Here you can order a bunch of live rock that can really come in with a lot of life! You can see here in this picture how much life comes with these rocks. Buying a large amount of live rock will help cycle your tank much faster than just a single live rock will.

A live rock with algae. Photo from Tampa Bay Saltwater

Tampa Bay Saltwater has built a great reputation for selling quality live rock at an affordable price. I should mention here that I am not paid by them to advertise! I believe they carry quality rocks and would recommend them to any of my friends. A quick search online will tell a story about excellent products and customer service. They can be found here

Reef Tank

This is what most people picture as a regular saltwater tank. They picture corals and mountains of rocks creating a complicated slice of the ocean in your house. This is the most complicated system in saltwater but also considered to be the pinnacle of saltwater keeping. To keep a reef tank you have to start with at least a FOWLR type of tank. You need some rock first as that is where the corals will be placed later. This type of tank also requires more, often higher end, equipment.

Reef tank. Photo from Tampa Bay Saltwater

Equipment needed for a reef tank
There are a few things that are absolutely necessary and a few things that are nice to have. One thing you must have is a good coral light system. You can find a nice article covering types of lights here

Another absolutely thing needed is a water filter. I don’t mean the water you get from your fridge but an actual reverse osmosis system. You can buy higher end units or something small like the RO Buddie from Amazon. This filters your water really well and removes something like 90% of all contaminants in your water. This includes chlorine, heavy metals, organic minerals and others. To take this to the next step you add DI resin. DI resin strips your water of everything and gives you only pure H2O in the end. This is great for a reef tank because you don’t want unwanted minerals building up in your tank. Most home systems use copper pipes and that copper does slowly leech into the water. While copper is a natural element in the ocean, in slightly elevated levels it becomes lethal to all invertebrates, corals, and even some fish.

Ro Buddie, photo from Amazon

Onto some of the more nice things to have but not completly needed at start up. One of those is a protein skimmer, which will be covered in more detail in another article. Have you ever been to a beach and seen some foam on the shore? That is what a protein skimmer does in our tank – it creates foam. By mixing water and air together it captures the organic waste and pulls up into a holding cup to be disposed of. They are a great feature and will be needed at some point while having a reef tank.

Protein skimmer in action in my tank

Another optional piece of equipment is an automatic water top off system called ATO for short. Every day you have to top off your tank with fresh water to keep the salt levels the same. An ATO does that for you. Each time the sensor activates it pulls a little fresh water into the tank keeping the salinity from ever rising.

An ATO unit like this connects to a pump to maintain salt levels



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