Converting a Freshwater Aquarium to Saltwater

at 2:00 pm

You are an avid freshwater fish keeper. You have mastered the small community tank with tetras, barbs, and various gourami’s and angelfish. You are versed in keeping the larger more aggressive cichlids whether they be African or Central/South American. Now you’ve found interest in the Marine world. You’d like to start a saltwater aquarium for the first time but you have no idea where to start or what types of questions to ask. I can help you. I’m certainly no marine biologist or deep sea diving enthusiast, but I have been in your shoes and I know what you need to know. The following will be an overview of making the transition from running a freshwater tank to beginning a saltwater tank. There is a ton of information out there and if you feel up to the read, please do. More knowledge certainly cannot hurt you. But if you want some of the basics of filtration, skimming, lighting, and live stock I’ll share my point of view with you. The first thing we need to establish is what type of saltwater tank you want to set up.

Where do I start?

Fish Only Tank
Let’s start out with the FO tank. FO stands for Fish Only. This tank is set up and maintained just like a freshwater setup in that you have a HOB filter, Canister filter, or sump for filtration and are stocked with fish and or invertebrates. This will be a farily low tech setup, but depending on the size of your tank you will still be able to keep many species of saltwater fish with success. Despite what you might think, many marine fishes are quite hardy and tolerate aquarium life well. Don’t get me wrong, there are certainly delicate species that need an expert’s hand but I think many people have this belief that all marine fish are extremely delicate and or sensitive which just isn’t the case. Bare minimum requirements: Aquarium, Lights, HOB/Canister/Sump filtration, Heater, Marine salt mix, Hydrometer, and a Test kit.

Fish Only With Live Rock (FOWLR)
Lets move on to the FOWLR tanks. This set up is pretty self explanatory. The basis is that the live rock functions as the filtration for the fish or fishes you choose to keep. Now if I’m getting ahead of you, stick with me because I will back track to the live rock. FOWLR setups are pretty simple as there really are no extravagant pieces of equipment that are necessary so in general these will be less expensive to set up and maintain. They also look a lot more natural. The rock itself gives the tank a nice reef-like look that really no decorations can mimic. The minimum requirements being: Aquarium, Lights, Power head(s), Live Rock, Heater, Marine salt mix, Hydrometer, and a Test Kit. You do not need a skimmer for a FOWLR tank, but they do have their benefits which I will also come back to.

Reef Tank

The Reef Tank. The mother load. The top shelf vodka. Perhaps I am biased but if you ask me, this is where the party is. Reef tanks can be some of the most beautiful aquariums in the world period. They are bursting with color and every inch of them can be full of life. What kind of life you say? Corals. There are definitely other forms of life on coral reefs, but the main focus of a marine reef tank is definitely the corals. They come in all shapes, sizes and colors you could imagine and then some. Some pulse with life even in the absence of water current, and some can stretch out and grab their food with tentacles. Many even fluoresce under moonlights, and all have the potential to catch your eye from across the room. But this extremely aesthetically pleasing glass box doesn’t come without it’s prices. In fact I’m just going to come out and say it… it’s expensive. Of course if you have patience and are determined you can find used equipment in decent shape and find sales online or bargain with people who are needing to get out of the hobby in a hurry. But don’t kid yourself. A reef tank is going to run you several hundred dollars by the end, and you can certainly spend a couple of grand if you want the ‘latest and greatest’ items. The needs and essentials for a reef tank can vary greatly depending on the types of corals you keep.

Reef Tank, courtesy of Mike LaHart

Still not really sure what you want to do? Lets touch on some of the differences between these tanks so you know what you’re getting into.

Live Rock
Live Rock is really the foundation of a marine tank. Even though it’s not necessary for a marine tank to function (ie the FO tank), I think it adds to the tank in many ways. Not only does it provide biological filtration for your aquarium, but it can also provide homes and protection for fish, invertebrates and corals. It also makes your tank look like a natural reef environment. Now you might be wondering why live rock can be so beneficial, but a river rock is well, just a rock. The answer is this- live rock is extremely porous. It’s so porous that it contains an exponential amount of surface area in comparison to a river rock. This surface area provides a perfect habitat for our coveted beneficial bacteria and some believe it can even provide habitat for nitrifying bacteria.

There are two types of live rock sold that you need to know about – Cured and Uncured. Cured live rock contains live beneficial bacteria cultures in the rock. This means it must be in a tank with proper heat, light, and salinity to ensure survival of the bacteria. Cured live rock will cost you more, because you don’t have to cycle it; it already contains the bacteria so all you need to do (theoretically) is transport it to your aquarium and you’re ready for live stock. Unfortunately, there is no way to know if the rock being sold to you is actually cured. Some stores may just put dried out rock into a tank and call it cured; hopefully this is not the case. Uncured rock is just that, rock that can function as live rock but is dried out or does not currently house any beneficial bacteria. Buying uncured rock, or dry rock is going to be much cheaper but you will have to cycle the tank and rock yourself.

Protein Skimmer

Protein Skimmers are definitely a piece of equipment that falls into the gray area of defined benefits. You will certainly come across people who swear by them and would never run a tank without them, and you will also come across people who feel that they are not necessary. Protein skimmers work by a process called foam fractioning. Basically by agitating the water and creating bubbles in a vertical column, proteins, wastes, and other free floating particles are carried upward with the bubbles to a collection area. When the bubbles burst the proteins and wastes are separated from the water and are left in the collection cup to be discarded. This keeps excess organics out of the water column lessening the chance for nuisance algae out breaks. It can also help keep the water crystal clear by eliminating debris. Conversely, skimmers can rob certain corals of beneficial nutrients that they would otherwise gain from by filter feeding. Zoanthids are a filter feeder that many claim benefit from dirty water. Overall, I think skimmers have their place in certain marine tanks. Lightly stocked FO or FOWLR tanks probably can go without a skimmer. Even certain reef tanks can flourish without a skimmer as long as care is taken to keep water parameters in check. Heavily stocked FO and FOWLR tanks or most reef tanks in general should have a skimmer IMO.

Reverse Osmosis De-Ionization (RODI)

RODI Unit stands for Reverse Osmosis De-Ionization. It’s a unit that purifies water by filtering out particulates and dissolved solids on a molecular level. Water is forced through this filter and passes through semi-permeable membranes that allow only the smallest molecules to pass (e.g. Hydrogen and Oxygen) leaving you with a cleaner purified water source. RODI’s can eliminate chlorine, chloramines, heavy metals, calcium, phosphates, and even nitrates. Reducing the TDS value (Total dissolved solids) will help keep nuisance algaes at bay by eliminating their nutrient source. The infamous Cyanobacteria or Red slime algae is known to feed on phosphates, silicates, and nitrates. Do I need one? – If you are setting up a future reef tank, yes you need one. If you are only setting up a FO or a FOWLR tank… no, probably not necessary. If you are on well water, then you should think about a RODI Unit. Your water source will be much more suceptible to fluctuation, especially in the spring and a RODI will eliminate high nitrates and heavy metal concentrations.

Tank Lighting

Lighting is another aspect that will vary heavily depending on what type of tank you choose. If you only desire to keep a FO or FOWLR tank, then lighting isn’t as important as if you were keeping a reef tank. If you are going to stick with a FO or FOWLR tank then any type of lighting will do – T5, T8, Compact Flourescent, LED, Metal Halides, or any High output bulbs. You’re going to find very quickly that lighting can become expensive. Especially the latter – LED’s, Metal Halides, and High output fixtures. So it’s really not necessary to use those types of lights for FO or FOWLR tanks. I do want to add this: Your bulbs should be a 10,000K+ spectrum and an Actinic bulb. You should be able to find replacement bulbs in the proper spectrum no matter what type they are. Reef tanks will need more intense lighting. T5HO, Metal Halides and LED’s seem to be the most popular. The specific wattage or PAR necessary for your tank will depend on the tank dimensions, mostly the depth. I’m not going to get into all of the details of lighting needed for a reef tank simply because it’s a vast topic. Just know that if you desire a reef tank you’ll need to research the types of corals you want to keep and find out what needs they have for lighting and go from there.

Hopefully, the information given here has helped you make a decision. Once you’ve decided what type of tank you want, we can move on.

The Tear down/ Setup

Now that you’ve decided what type of tank you want, lets walk through the actual switch. I took my 29g freshwater setup down not too long ago, so I’ve put together a step-by-step guide to make your transition easier.

This is my 29g tank before I switched. It was a great sized community tank. I kept everything from a breeding pair of Convicts, to tetras, barbs, and rainbowfish, to fancy plecos, loaches and bichirs. The tank had a Marineland Penguin 150, and a Marineland Magnum HOT filter. The light fixture is a 18 watt T5 with a Colormax bulb and a 6700K white bulb.

I started by returning all of my fish to the pet store. I received some store credit, but mostly I wanted them to go to a good home. I drained the tank completely, and removed the decor, substrate, and equipment. The beneficial bacteria that thrives in your filters will not transfer over to a saltwater environment. So if you thought you could save a lot of time by saving the filter media and using it on your new saltwater tank, sorry no short cuts. Nice try though. As I’ve heard many times when referring to marine tanks “Nothing good happens fast in this hobby”.

I took the opportunity to give the tank a good scrub down. I just used an algae scraper and some tap water and went to town. Once I had the tank squeaky clean, I rinsed it out one more time and slapped a new background on it. I planned to do a FOWLR tank, so I used the same light fixture but swapped out the 6700K and Colormax bulbs to a 10,000K bulb and an Actinic bulb. This combination gives off more blue and provides a much more natural ocean look to the tank. Actinic bulbs also promote coralline algae growth which is beneficial to any marine environment.

Next, I added a 20lb bag of sand. I thoroughly rinsed it before hand of course. I had also purchased a BRS RODI Unit (Bulk Reef Supply Reverse Osmosis De-Ionization) and filtered water for the tank. It took me a while (the RODI filters yields 75 gallons of RO per 24 hours) but I slowly filled the tank with RO water and then turned on my new Koralia powerheads and CPR BakPak protein skimmer. I added salt mix (Instant Ocean Reef Crystals) to bring the salinity up to 1.026 specific gravity. I used a cheap plastic hydrometer to test the salinity and with a little patience I got it just right.

Once the salinity and temperature were where I wanted them to be (79 degrees F, 1.026 SG), I went to my LFS and picked out some live rock.

I let things settle over night and the tank really cleared up nicely.

Once the live rock was in the tank and everything was running smoothly I began testing the water. I purchased Cured live rock, but as stated above there is really no way to know if the rock is in fact cured. So I began ‘feeding’ the tank. I used sinking fish pellets as a source of ammonia. I put in a pinch or two every day for a week straight and tested every day. As the food begins breaking down it becomes ammonia. If the live rock is cured, the ammonia will immediately be broken down into nitrites, and nitrites into nitrates. If not, then the tests would show an increased level of ammonia. Anything above 0ppm is unacceptable. As it turns out the live rock I purchased was cured. I tested every day for a week, and for the first 5 days or so, nothing was present. No detectable traces of Ammonia, Nitrites, or Nitrates. After day 6, I registered about 5-10ppm Nitrates which means the beneficial bacteria was doing its job. After a large water change, bringing the Nitrates down to 0ppm or as close as possible I was ready for my first live stock.

This has been a brief overview of what I feel are relevant subjects for new marine enthusiasts. I hope that you have gained enough knowledge from this information to take yourself to the next step in setting up your own marine environment. There is plenty of information available on the net, so if you still feel uneasy about certain topics feel free to ask questions or do additional research. You can also join the forum and PM me or any of our advice team for more information. I look forward to meeting any new future reefers on the forum!

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