Calling All Freshwater Keepers, You Can Make the Switch!

Making the switch from freshwater to saltwater isn't as daunting as you may think

Making the switch from freshwater to saltwater isn’t as daunting as you may think

I’ve kept freshwater aquariums before, but saltwater aquariums? Aren’t they really difficult?”

Chris and I frequently hear comments like this from non-hobbyists as well as from freshwater aquarists who are contemplating making the saltwater switch. The prevailing impression among the uninitiated seems to be that keeping a saltwater aquarium with any degree of success demands an extraordinary level of skill and experience. But nothing could be further from the truth.

If you’ve developed the necessary skills to maintain a freshwater aquarium, there’s nothing to stop you from succeeding with a saltwater tank. Sure, you’ll need to familiarize yourself with a few new concepts and techniques—and maybe a new gadget or two—but virtually all the knowledge you’ve acquired as a freshwater fishkeeper will transfer.

What’s different?

So, what are some of the new techniques, materials, and equipment you’ll need to become familiar with before setting up a basic fish-only saltwater system?

The salt water itself

The most obvious is the salt water you’ll use to fill the tank initially and to replace any water removed during routine water changes (water lost to evaporation is replaced with fresh water). This is a simple matter of mixing synthetic sea salt into conditioned tap water (we recommend RO/DI water) and measuring samples with a refractometer or hydrometer until the desired salinity level is achieved.

Live rock

The material known as “live rock” is another thing you’ll need to learn about that doesn’t exactly have a counterpart on the freshwater side of the hobby. Not truly alive but harboring all kinds encrusting organisms, live rock is used by most saltwater hobbyists to provide biological filtration, to create a natural reef-like structure for their livestock, and to increase the overall biodiversity of their systems.

Substrate materials

Forget those decorative gravels so popular in freshwater fishkeeping. Calcareous materials (e.g., aragonite) of various particle sizes are the substrates of choice for saltwater systems.

The protein skimmer

While you’ll hear mention of all kinds of high-tech gizmos and gadgets used on the saltwater side of the hobby, one essential piece of equipment you may not be familiar with is the protein skimmer. This device mixes air bubbles and water in a reaction chamber to strip out dissolved organic compounds before they have a chance to decompose and pollute the water. In our opinion, this is one piece of equipment no saltwater hobbyist should be without. No other device is more helpful in maintaining the exceptional water quality that sensitive marine organisms demand.

What stays the same?

Notwithstanding these few differences, much of what you already know, do, or are using now can make the saltwater switch with you, including:

Is anything on the saltwater side easier?

Believe it or not, at least one aspect of aquarium keeping is actually easier for saltwater hobbyists than it is for their freshwater counterparts—providing species-appropriate water chemistry. Whereas freshwater species can differ markedly in their requirements with respect to pH, water hardness, etc., the vast majority of marine specimens on the market are collected from coral reefs with virtually identical water parameters. All the constituents dissolved in natural sea water are present in correct proportions in any high-quality sea salt mix. All you have to do to provide the right conditions is mix the salt with conditioned tap water, aerate it, and heat it to the desired temperature.

Have you made the switch?

If you’ve already made the switch from freshwater to saltwater aquarium keeping and have any thoughts or experiences to add (or if you can think of something we’ve missed), we’d love to hear from you in the comment section below!

Photo Credit: Mr. Sepia & Clevergrrl


If you enjoyed this post, subscribe to get our new posts in your email.
About Jeff Kurtz

Jeff Kurtz is the Co-founder/Editor of Saltwater Smarts, former Senior Consulting Editor for Tropical Fish Hobbyist Magazine, and the aquarist formerly known as “The Salt Creep.” He has been an aquarium hobbyist for over 30 years and is an avid scuba diver.


  1. Alex Ingalls says

    I think you should change the part about tap water. Really you cannot condition tap water to be safe for even a fish only saltwater tank. You should replace that with RO/DI or distilled water that is free of copper and reads 0 TDS.

    • Jeff Kurtz says

      That’s great advice, Alex! Using RO/DI-purified or distilled (and copper-free) tap water will eliminate any guesswork about “what’s in there” and will give you the greatest degree of control over your water quality.

    • Chris Aldrich says

      Good point, Alex. Our recommendation here at SWS is always RO/DI, though we have seen folks maintain healthy FOWLR and even reef aquariums [gasp!] with tap water. Of course much of that success can be attributed to better than average source water (highly variable between municipalities), as well as diligent water changes and maintenance.

      We are definitely on the same page, though. Why not start with the best water you can?

      • Alex Ingalls says

        Fair enough. Yes it can be done with tap water but your right that it does depend on the quality of it 🙂 I have seen people do it too but I have seen many people crash their tanks from it also. I just helped out a local friend and when we went to test her FOWLR tank for phosphate i put in the first set of drops from bottle #1 and it went off the charts let alone even getting in the second bottle thats supposed to make the color change haha. And there are fish out there that are much heartier then others. When I worked at the local petco we could not keep any sharks in because the pipes from their RO/DI unit consisted on copper piping. The store manager ended up getting mad that I refused to order them but I absolutely would not order a fish I knew was coming in to its death. I would only special order them for people that wanted them and have them come get them right when we got the shipment so they could go straight from the bag into their water rather then sit in our “toxic” water. 🙂 Plus with technology these days you can get a decent RO/DI unit for fairly cheap and the replacement media isnt all the spendy. Good Luck to anyone who starts a saltwater/reef tank I hope you succeed because it is well worth the extra time they take to maintain!!!

  2. ok 25 years ago had a freshwater community tank which I run for 5 years had no problems, went onto fish only marine tank run for 3 years no problems, had a break from fish keeping for quite a few years 2 years ago bought a redsea max 130d to set a reef tank up but found it very expensive far too much water testing and adding supplements every day when I was working long hours so I have gone back to freshwater planted tank with a few fish running now for three months so easy to run, so what you are saying in my opinion is not as easy as you say, only my opinion

    • Jeff Kurtz says

      Thanks for your insights, Kel! Sorry your experience with reefkeeping wasn’t so positive, and we hope we can persuade you to come back to the salty side at some point in the future (obviously when your schedule and budget allow).

      We’re definitely not suggesting that reef systems aren’t challenging or that saltwater aquariums in general are necessarily easy–just that the saltwater side of the hobby isn’t as difficult or mysterious as many people are led to believe and that many of the same skills and principles that are necessary for success with freshwater tanks apply to saltwater tanks, as well.

      Of course, just as with the different types of freshwater systems, some types of marine systems are more challenging than others (from a freshwater perspective, think discus versus platies or high-tech planted tanks versus fish-only).

      Also, you did maintain a fish-only marine tank with no problems for three years. That suggests you have the skills for marine fishkeeping and know how to apply them. So, again, we hope you won’t let your last frustrating experience sour you on saltwater tanks forever.

      • Thanks for you’re insight on how you see things , at the time I had the reef tank long hours at work made it much harder to keep the reef stable , I hope I have not put people of the fantastic hobby but I hope anyone going into reef keeping understands you have to have more time to succeed reef keeping.

        • Jeff Kurtz says

          So true, Kelvin! And thanks again for your thoughts. They’ll, no doubt, encourage aspiring reefkeepers to go into that aspect of the hobby with their eyes wide open.

Leave a Reply to Jeff Kurtz Cancel reply