40 Gallon Tank Need Advice On Setup And Possible Stock


Hello all! So recently I promised my wife that I would set up a salt water tank for her, and currently am researching possible options for her. I have experience running freshwater tanks, but am finding with research that saltwater is a different league unto itself.

Right now I have a 40 gallon breeder that I plan on using. I'm looking at getting a Fluval C3 or C4 power filter along with a Fluval PS1 Protein Skimmer for filtration and then a solid water heater. I'm also weighing the benefit of throwing a fluval canister filter in place of the power filter. We are considering setting up a reef tank.

There's a couple of possible options that we're looking at. One option that we're considering is getting two ocellaris clowns and a 6-line wrasse. One question I have is regarding capacity. We're wondering if we could also add one or two skunk shrimps and a banggaI cardinalfish without overcrowding the tank?

Another alternative we're considering is getting two ocellaris clowns and a mandarin goby. We've looked at the mandarin goby, we like it, but I'm concerned that with 40 gallons we may not be able to provide a constant supply of copepods and other critters. I've looked at a CPR AquaFuge2 refugium (I like the hang off the back idea) as a possibility, but am wondering that if setup good with liverock, algae, and copepods, if it could produce enough supply for a Mandarin Goby? If so, does someone have a cheaper suggestion?

Thank you ahead of time.


You are correct about saltwater being quite a bit different. In point of fact there are a number of "Bad Habits" that need to be shed from the freshwater side when doing a saltwater tank. Here are some things to know:

1) I would avoid a canister filter on the tank, in marine environments they have a tendency to trap the nasties and can be very labor intensive in order to avoid them becoming nitrate factories. An open filtration system that is easy to clean and maintain is definitely preferred and the Fluval HOB you mentioned is a great choice since there are many options with them.

2) Treated Tapwater is fine for a freshwater tank but especially for reef tanks it is often not recommended since the minerals/solids in tap water can cause long term issues with reef system (ie out of control algae issues, things that can affect corals). To counter this it's highly recommended to use an RODI system (Reverse Osmosis with a De-Ionizer) this strips all the solids out of the tap water to give you 0 TDS (Total Dissolved Solids). You then re-mineralize with the specific marine aquarium salt (ie Instant Ocean, Red Sea, etc.) which has strictly the beneficial minerals for a marine tank with none of the errant nasties. You can buy the water from your LFS (Local Fish Store) in most cases, but it will probably be cheaper in the long run for you to have an RODI system of your own. Aquatic Life RO Buddie is a 4 stage RODI unit that can be had for around $60 from Amazon:

If you live in an area with a really high TDS you may want to get a nicer 5-6 stage unit but the price ranges for $130-$150 on those units.

3) Unlike Freshwater the Biofilter isn't maintained in the filter media, it is maintained in the Live Rock (or you can get dead Live Rock aka Dry Rock and seed it with bacteria to become live again if you want to save some money). This is why Live Rock is so crucial to saltwater tanks as it is the biofilter for the tank

4) Unlike Freshwater Evaporation is a much bigger issue with Saltwater tanks since Water Evaporates but Salt doesn't. Therefore in order to keep your salinity stable and to not rise to deadly levels for your fish and corals you need to top up your tank with Fresh RODI water.

5) While you may have gotten very accustomed to the likes of an API test kit for Freshwater, you really should go with something more accurate for Saltwater/Reef (ie Red Sea or Salifert). The API Nitrate test is almost worthless for a reef tank and they can give false positives for Ammonia.

6) If you do an HOB Protein Skimmer, be aware that many are marginal in their effectiveness. The only ones I feel comfortable in recommending for HOB are the Eshoppes PSK-75H or 100H models or the Reef Octopus Classic 100.

7) The Fluval Filters can be modified into refugiums and you can do biofiltration (ie Chaeto) which also happens to be the perfect breeding ground for copepods

8) I strongly suggest avoiding the Mandarin Goby as they need to feed near constantly and a 40 gallon tank simply doesn't have the ability to produce a breeding population big enough to keep a single mandarin fed. With Mandarins it's less about the tank size and more about the amount of live rock, chaeto, etc. that is required to maintain a self sustaining/breeding population of pods. You need at least 75lbs of Live Rock to sustain them and it simply isn't feasible with a 40 gallon tank. Take it from a guy who tried and failed with a green mandarin and ended up spending nearly $300 to try and keep it fed only to have it die in just under 3 months. Mine also adapted to frozen food as well and I simply couldn't keep up with the multiple times a day feeding they require to stay healthy (and neither can anyone else who goes to school full time or works a full time job). There is a reason why sites list it's care level as "Difficult"

9) You will need a powerhead/wavemaker to simulate underwater current (above all please don't put a bubbler in there as it does nothing for a marine tank) and a refractometer to measure salinity levels

10) Make sure the tank heater you get is an adjustable tank heater suited for marine environments. Most are good for both salt and freshwater but there are a few fixed temp heaters (ie Aqueon and Tetra) that have an enamel coating that will peel off in a saltwater tank (happened to me on my first tank). Eheim Jager makes some decent cheap tank heaters that are good for both environments.

11) I would avoid any goofy fake plants, decorations, etc. as they generally aren't designed for saltwater and won't release good things in the tank (Many folks coming over from freshwater make this mistake). Let the corals and your rockscape be your decorations.

12) A 40 gallon breeder is an excellent starter choice for a saltwater tank as it's big enough to give you some options without being so big to be super cumbersome (ie adding in more equipment like a sump, return pump, skimmer, etc.), it's also big enough to be relatively stable for water parameters. For future reference, length followed by width are arguably the most important dimensions when it comes to increasing options for saltwater fish, so always go with a tank that maximizes those dimensions (height is the least useful).

For reference and ideas here is my old 36 gallon bowfront which would be somewhat comparable with equipment for your 40 breeder and has an HOB Skimmer in action:

13) For lighting, when it comes to corals and 'nems, going really cheap IS NOT an option. Plan on spending at least $200 to get good lighting to your corals. An option that would work would be something like this:

or if you want a bit more controls (ie Timer) then this variant will work:

Be aware those lights are super powerful and you will want to mount them at least 18 inches above your tank and keep the intensity down

I know that it's a lot to take in but there is a lot to be learned before going salty. One thing I always tell folks looking into a saltwater tank is to never overlook wrasses. They are full of color, personality and make great additions to tanks. For a 40 breeder I would recommend the Lubbock's aka Tri-Color or Multicolor Fairy Wrasse. Pictures don't do it justice:


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