Stocking My 29G Brackish Tank

[Ceramicbull]

This is more or less a rehash of a post I put in the "My First Freshwater Tank" forum by mistake, sort of. I am starting my first tank, but I decided to go brackish. So long as you can stand a neophyte in your presence, I'd like to ask your opinion of my stocking plans. I'll try to condense all of the relevant info into this post so you won't have to leave the page if you don't want. At the moment my tank is at 1.008 SG (edit: at about 77F, or 25C for you metric types) and I have 3 Dalmatian Mollies in there for the cycle. They seem happy and healthy, and the nitrites are ever so close to trace levels: it's almost time to go shopping. For the other tankmates I'd like to add:

2x Knight Gobies
1x "Freshwater" Flounder/Lined Sole (most likely Achirus lineatus)
2x Orange Chromides
and an Olive Nerite Snail (kept forgetting about that in the previous post.)
(don't forget I already have the 3 Mollies)

I have an over-capacity filter and a couple Java Ferns as well. From what I've read the above species are peaceable with each other, so long as none will fit in any other's mouth. But, will they be happy together in a 29g tank in those numbers?

For feeding the sole, I figure I'd just get a rigid, narrow, and hopefully transparent plastic or glass tube and funnel the brine shrimp/whatever down to the thing. Another idea I had was a turkey baster: suck some tank water, squirt in dish, add brine shrimp, suck back up, deliver to fish. Awful ideas? Beats paying $20 for a "target feeder"?

I also have a concern regarding the pH requirements of the Mollies and the Chromides: the plurality of my google-research suggests Mollies can stand pH up to only 7.8, but Chromides no lower than 8. There are others suggesting that Chromides can go as low as 7 and Mollies up to 8.5 (and a few specifically mentioning Mollies and Chromides as tankmates), but I'd rather ask than be sorry later. (my current pH is 7.8)

Also, I've had a devil of a time finding the Chromides, so at the moment I'm only going off of Youtube videos and a desire to find something with a bit more color and more traditional form. If I can't find the things, the question is moot, so any suggestions for alternatives are welcome. I've also seen a cryptic reference to Chromides being available in Spring, but I can't find it again. Perhaps they're seasonal?

Thanks for your input,

C-Bull

 

[nmonks]

SG 1.008 at 25 C is overkill for the livestock you have; I'd be aiming for SG 1.003, if only to cut costs and ensure good plant growth.

Flatfish are nocturnal, so provided you put the live or wet-frozen bloodworms, mosquito larvae and so on out at night, he should feed by himself. They do prefer wormy foods, and adult brine shrimp are famously low in nutrients and so of no value at all as a staple. I've had flounders feed on trout pellets during the day, but only once they were settled in.

Orange chromides inhabit fresh and brackish water, and will do well in both. Much like mollies really. SG 1.003, pH 7.5, moderately hard water is fine for both. I happen to find the wild-type orange chromides much more attractive than the bright orange artificial form. One nice thing about the wild-type fish their colours change dramatically with mood, especially when spawning. It's quite something to see.

There are any number of brackish water cichlids -- see my FAQ for my current list -- but few make good community fish, especially not in a 30 gallon tank. Do bear in mind that orange chromides and knight gobies are both territorial, so there's going to be a bit of conflict between them if you don't provide sufficient hiding places.

Cheers, Neale

 

[Ceramicbull]

SG 1.008 at 25 C is overkill for the livestock you have; I'd be aiming for SG 1.003, if only to cut costs and ensure good plant growth.

Thanks much, is there any rule of thumb for lowering my salt content while I change water? Will there be any problem with just not adding any salt to the new water until I get it that low? Come to think of it, I really have no idea why I put it that high in the first place. More brackish is more awesome or something macho (dumb) probably.

The wild type chromides sound fantastic, and when I do get them (my LFS said he could get them in 4 days without problem) I'll definitely go that way.

Thanks again,

C-Bull

 

[nmonks]

I'd do water changes with brackish water at SG 1.003. That'd gradually lower the salinity. You don't want to make any sudden changes because of the risk of stressing the filter bacteria.

Cheers, Neale

Thanks much, is there any rule of thumb for lowering my salt content while I change water? Will there be any problem with just not adding any salt to the new water until I get it that low?

 

[Ceramicbull]

Flatfish are nocturnal, so provided you put the live or wet-frozen bloodworms, mosquito larvae and so on out at night, he should feed by himself. They do prefer wormy foods, and adult brine shrimp are famously low in nutrients and so of no value at all as a staple. I've had flounders feed on trout pellets during the day, but only once they were settled in.

Well, a day in with the new fish, the gobies and mollies seem to get along just fine. The Nerite has been grazing contently on the bogwood, and the flounder has been doing a fantastic job at hide and seek with me (it is winning). I'll add the Chromides after I am confident in the water chemistry. I threw in a few mysis shrimp after turning out the lights, but I can't say as I saw him eat. There weren't any in the tank this morning, but the gobies and one of the mollies enjoy the mysis, so I have no idea. Would it be better to wait until a few hours after the light is off to guarantee that the other fish aren't as aware?

In general, how often and how much do I need to feed the carnivores? I found one source that suggested "twice a week" for the flounder but nothing on the knights, nothing in terms of quantity. My LFS suggested hikari mysis, and those come in 3.125g cubes. One cube seems like way too much.

Thanks,

C-Bull

 

[nmonks]

Flatfish really need nightly feeding. They are very prone to starving. Offer a variety of foods -- worms, shrimps, chopped seafood. They hunt mostly by smell, remarkably enough, so aren't too fussy.

Cheers, Neale

In general, how often and how much do I need to feed the carnivores? I found one source that suggested "twice a week" for the flounder but nothing on the knights, nothing in terms of quantity. My LFS suggested hikari mysis, and those come in 3.125g cubes. One cube seems like way too much.

 

[Ceramicbull]

Well, night 2 hasn't gone terribly well either. I dropped some in after keeping the tank (and the surrounding room) dark for an hour, and the flounder remained anchored to the wall while the gobies gulped everything down. I'll see if I cant find something live and worm-like tomorrow. It's a fascinating fish, but are the gobies just too competitive for me to keep him well? Perhaps it's just the new environment? How long would you give it before I should just return it? It was at the petshop for at least 2 weeks, so it must have been eating there. Was in with some purple spot grudgeon and some weird transparent things that looked like a cross between a catfish and a shrimp. Mabye I'll drop by and ask what/how they fed him as well.

Thanks,

C-Bull

Flatfish really need nightly feeding. They are very prone to starving. Offer a variety of foods -- worms, shrimps, chopped seafood. They hunt mostly by smell, remarkably enough, so aren't too fussy.

Cheers, Neale

Edit: removed double post

 

[nmonks]

Flounders and gobies should coexist, and I have kept them together. But there's much to be said for getting the flounder feeding first, and once he's settled in, then adding tankmates. If you can confine or remove the gobies somehow, that'd be a plus.

Cheers, Neale

Well, night 2 hasn't gone terribly well either. I dropped some in after keeping the tank (and the surrounding room) dark for an hour, and the flounder remained anchored to the wall while the gobies gulped everything down. I'll see if I cant find something live and worm-like tomorrow. It's a fascinating fish, but are the gobies just too competitive for me to keep him well? Perhaps it's just the new environment? How long would you give it before I should just return it?

 

[Ceramicbull]

Managed to get it to eat a few bloodworms by dangling them in front of him while the lights were off. Not a resounding victory, but I'll take it where I can get it for now. It sounds like they get more comfortable and assertive food-wise as they go. If I'd read your FAQ earlier I probably would have used the flounder to cycle the tank rather than the mollies: that way it would have gotten comfortable without any competition.

Thanks for all the help,

C-Bull

Flounders and gobies should coexist, and I have kept them together. But there's much to be said for getting the flounder feeding first, and once he's settled in, then adding tankmates. If you can confine or remove the gobies somehow, that'd be a plus.

Cheers, Neale

 

[nmonks]

At least he's eating, and that's a significant milestone. Well done! Most folks don't even get that far.

Good luck, Neale

Managed to get it to eat a few bloodworms by dangling them in front of him while the lights were off. Not a resounding victory, but I'll take it where I can get it for now. It sounds like they get more comfortable and assertive food-wise as they go. If I'd read your FAQ earlier I probably would have used the flounder to cycle the tank rather than the mollies: that way it would have gotten comfortable without any competition.

Thanks for all the help,

 

[Ceramicbull]

I'd do water changes with brackish water at SG 1.003. That'd gradually lower the salinity. You don't want to make any sudden changes because of the risk of stressing the filter bacteria.

Quick Question: I just noticed that my tap water tests at somewhere above 1.000. I would guess because of hardness rather than any actual salt. When I adjust for what's in the tap water (I assume I do need to adjust), is it a straight addition (example: 1.004 hydrometer reading - 1.001 tap water reading = 1.003 SG due to salinity) or is the math more complex than that?

 

[nmonks]

Yes, the maths is complicated! Fish (and plants, and filter bacteria) actually react to salinity, i.e., the concentration of salt in water. So strictly speaking, you should be adding a certain amount of salt to the water. For a low-end brackish system, something between four and nine grammes of marine salt mix per litre is about right, resulting in salinities equivalent to 10-25% the salinity of normal seawater.

Now, the thing is that specific gravity is the density of water, and it depends on temperature and air pressure. Air pressure isn't a big deal unless you live at the top of a mountain, but water temperature can be a major factor, especially if you add the salt mix to cold tap water. Density goes up as temperature goes down. So if you add 4 grammes of marine salt mix to 1 litre of water, you get about SG 1.001 at 25 degrees C, but SG 1.003 at 15 degrees C.

If you look on my web site there's a program for Mac and Windows called Brack Calc that demonstrates how this works.

A further problem is that hobbyist hydrometers and refractometers don't give very accurate results. It's worth observing that even the $50 refractometers some marine aquarists go on about aren't very accurate; scientific-grade units cost $1000 upwards, so you can well imagine the cheap ones sold on eBay are very much the basic model.

With all this said, the short answer is that it doesn't matter massively if you're "off" a bit. Brackish water fish by definition tolerate variation, and the main thing is that you don't add so much salt that the plants and filter bacteria get stressed. I'd suggest weighing out some salt first, then taking the specific gravity, making a note of that value, and simply repeating that in future. Suppose you make up 10 litres of water at close to the aquarium temperature. Add the appropriate amount of marine salt mix. Suppose you need to add 4 grammes per litre, you'd add 4 x 10 = 40 grammes. Stir well. Wait a few minutes for it to fully dissolve and then stir again. Then use your hydrometer -- correctly! -- and make a note of whatever specific gravity you get. Don't worry if the specific gravity seems "wrong" -- it's more likely the hydrometer is off a point or two. Write down the result onto the side of the salt box with a marker pen, and that's that!

Cheers, Neale

Quick Question: I just noticed that my tap water tests at somewhere above 1.000. I would guess because of hardness rather than any actual salt. When I adjust for what's in the tap water (I assume I do need to adjust), is it a straight addition (example: 1.004 hydrometer reading - 1.001 tap water reading = 1.003 SG due to salinity) or is the math more complex than that?