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FAQs on Going from Brackish... to Marine Systems 

Related Articles: Converting from Freshwater to Marine Set-Up,

Related FAQs: Freshwater to Marine 1Freshwater to Marine 2,


brackish into marine      7/8/15
Greetings all!
First of all, thank you all for your excellent advice in the past. Much appreciated.
<Most welcome.>
I have a 150 gal (48" x 24" x 30") tall tank which I have, over the last three years, converted from a low-end brackish into a marine environment (now 1.022).
After acclimation, the tank has since been stocked with 10 mono sebae and a silver scat (argus). All are doing wonderfully even though I do feel I have created an overstocking issue. True?
<Depends on the size of the Scats and Monos. Assuming adults of both, Monos typically get to about 15 cm/6 inches under home aquarium conditions, Scats a bit more, maybe 20 cm/8 inches. So let's say 70 "inches of fish" altogether. At face value, you're not overstocked. But the inch-per-gallon rule applies to small, Guppy to Molly sized beasts, not big, messy fish like Monos and Scats. So being a bit more objective, then yes, you probably are overstocked. Water quality is your benchmark of course, with aquarium size simply an easy way to "guesstimate" the space needed for a certain fish assuming average levels of feeding, filtration and water changes.>
For filtration, I am currently using an Eheim 2229 canister as well as two AquaClear 110. Water changes are 20% every two weeks.
I have found that my nitrate levels have started to sneak up rather quickly in the past few months (40 to 70 by change time).
<Ah! There you go, really very high nitrates indeed, implying that while filtration might be working (keeping ammonia and nitrite at zero) the end product of that process (nitrate) accumulates very quickly. As a rule, you want below 50 mg/l for standard communities of freshwater or brackish species, and less than 20 mg/l for more sensitive species.>
I am looking at now starting to add some live rock and macro algae into the system. My main question is:
Will these be decimated by the, always hungry though well fed, inhabitants?
(also, not looking at adding any other inhabitants unless advised).
<Scats and Monos are both "reef safe" though Monos are predators (will eat any shrimp or fish they can catch) and Scats will graze any/all algae they can find. Nonetheless, you will see both species in public aquarium reef tanks.>
I was looking at using a smaller spare tank as a refugium but am running into space issues as well as hesitations with overflow boxes / flood potential. Also, I did not feel that the option of small 5 gal HOB fuges would provide much benefit for the cost. Same boat with a HOB skimmer.
The other tank in question is a 65 gal which is now at salt conditions with black sailfin mollies (five).
<Old school! I bet they're doing surprisingly well, aren't they?!>
I am toying with the idea of making this a "show tank" refugium. Mainly for its uniqueness. Would I run into issue with the mollies? If I were to eventually add a few clown fish with an anemone, would the mollies have issue with the invert?
<Mollies can/do get eaten by anemones. While tolerant of seawater salinity, they're not marine fish in the wild, at least, not beyond the very shallowest (few cm/couple inch) depths around harbour pilings, mangroves and the like. They wouldn't know an anemone from a rock, which makes them easy prey. On the other hand, they can thrive in FOWLR systems or even in sumps where there is adequate light for them to graze on algae and detritus.>
Been searching for answers and had not found anything substantial.
<Switching from brackish to marine was once very common, but less so now, so probably little on the Internet about it. Can work very well, and a school of Shark Catfish for example make a stunning addition to a large fish community alongside snappers and so on, and much easier to keep than "real" sharks despite looking so similar. On the other hand, some marine
fish will thrive at SG 1.018, which can be very economical if you simply want a fish-only or FOWLR system. It'll save you about 20% off your salt-making bill, and inhibits some marine parasites, but with the minus side being most invertebrates not adapting too well to reduced salinity, though a few -- Nerites and blue-leg hermits in particular -- are actually estuarine animals that do just fine under such conditions. Do see my Brackish FAQ if you haven't for more on the marine and brackish side of things.>
I knew you all could offer great advice. Thank you in advance,
<Bob may want to add something, but I hope this covers the basics. Cheers, Neale.>

SW stocking & filtration      1/21/15
Hello there. I have a 125 brackish set up that I plan on converting over to saltwater in the next few months. The tank currently has the following:
1 green spotted pufferfish
1 ruby scat
8 mono Sebaes
2 Columbian catfish
1 white crayfish
<These aren't brackish.>
3 black mollies

As The salinity of the water gets closer to seawater (around 1.015) I plan on returning everything back to my LFS except the scat, both catfishes, and three of the monos.
<Cool. Though the Puffer and Mollies would be fine in seawater (though how long either would survive alongside a Volitans Lionfish is debatable! So your choice here is a wise one.>
Once I finally get the salinity to 1.022 I plan on introducing the following:
1 black volitans lionfish
1 red cigar wrasse
1 orange shoulder tang
1 black edged moray eel
1 African starfish
3 squirrelfish

<An interesting mix of fish. Do think about the Squirrelfish carefully though; many species are happier at slightly lower temperatures than some other tropical marine fishes.>
I was wondering if this would be too overstocked because if so, I can easily get rid of the monos and the catfish but the mono is special to me.
<That's a lot of fish for a 125 gallon tank! The Cigar Wrasse alone gets to some 50 cm/20 inches in the wild, so even a 200 gallon tank would be somewhat cramped. If this was me, I'd stock somewhat slowly. I'd skip echinoderms and other invertebrates, at least initially, because they're much more delicate (with a few exceptions) than marine fish. A Scat; a pair
or trio of Monos (they often form pairs that work rather well); the Shark Cats would make good "carry overs"; add to these the Lionfish (an excellent companion for robust brackish water species); a peaceful and easy Moray like Echidna catenata would be my next choice; then if you want something active and midwater-y, then perhaps a snapper, tang or even a robust
Angelfish. One of the smaller groupers can work too, but not many are scaled for life in 125 gallons.>
Also, I am currently running two MarineLand penguin 350 filters that have a combined flow rate of 700 gph so I was wondering if this would be sufficient in keeping up with the bio-load in the aquarium or would I have to upgrade to something bigger.
<Do let me direct you to Bob's article on stocking marines.

Various links from there. Much fun to be had with fish-only systems, but would recommend aiming for the FOWLR avenue at some point, canisters alone being okay but not great for marines. In such systems brackish species can make interesting additions; Monos as dither fish for shyer species, Shark Cats as centrepiece predators. Cheers, Neale.>

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