Brackish Tank Questions; stkg., substrate, fdg.
Hi, I haven't had an aquarium in a while and I'm thinking about getting
back into the hobby. In particular, I'd like to start a low-end
(SG 1.002-1.003) brackish community tank in the 29 gallon
aquarium sitting empty in my basement. I have some questions relating to
stocking, substrate, and feeding.
First off, my tentative stocking plan is:
(1) Peacock spiny eel (Macrognathus siamensis) OR (1) Barred spiny eel
<Either should work here, though Macrognathus pancalus is arguably the
more truly brackish of these species. Neither will want much salt
though; 1.002 should be ample. Lower salinity will also ensure plants
can grow well, especially Indian Fern, a definite plus here for stopping
Spiny Eels from being jumpy.>
(1) Male and (2-3) female short-finned mollies
(2) Orange Chromides
<Generally fine, though as territorial as any other cichlid of this
(1-3) Knight gobies
<Nice fish, and will ensure no baby mollies survive!>
Would this be overstocked?
<Nope. Busy, yes; overstocked, no. Just keep on top of filtration and
I'm also concerned that in a 29, a pair of Chromides might become
tyrants if they decided to breed.
<Always a risk.>
If you think that would be the case, I'll either reduce the Chromides to
a singleton or remove them from the plan completely. (If you think this
setup would be overstocked, they're also my first choice on what to
eliminate.) I'm also wondering if even provided enough hiding spaces,
the 29 might be too small for multiple knight gobies. How many do you
think would be ideal for this setup?
<Two females and a male should be okay.>
On to substrate, I have a bag of CaribSea Sunset Gold sand laying around
my house. Would that be soft enough for the spiny eel, or should I stick
to buying some silica sand?
<I've not handled this brand of sand personally, but if it feels smooth
rather than sharp, it's probably fine. That said, pool filter
sand/smooth silica sand is so cheap, you might want to play it safe and
go straight for that.>
Additionally, what depth of sand would be best to allow the spiny eel
room to burrow but not to risk anaerobic decay? Does 2" sound about
As for feeding concerns, I want to make sure that the plant-based foods
for the mollies and the meat-based foods for the other species wouldn't
cause any health problems if the other party ate some of it. I also
some advice for feeding a balanced diet to the spiny eel and knight
I know that spiny eels go crazy for earthworms, and I suspect that the
knight goby would enjoy them, too.
<Yes! Very much so. Knight Gobies are very much predators.>
However, I'm a bit confused as to which of the big three in aquatic
feeder worms (bloodworms, blackworms, and Tubifex worms) is most
nutritious and least likely to carry diseases.
<Not much in it, to be honest. Tubifex have a very bad reputation,
probably justified. But bloodworms and blackworms aren't exactly
cultured in crystal clear pools of French mineral water! On the other
hand, if gamma
irradiated, they shouldn't carry any pathogens, and if used sparingly,
the risk from introducing heavy metals, for example, shouldn't be too
That said, marine aquarium foods like krill and fortified brine shrimp
are certainly safer and usually accepted readily.>
I've seen claims in favor of or against all three of them, even here on
Wet Web Media. I'd sort of like to start a culture of one of these in
one of the smaller empty tanks as an easy source of live food, but I
don't know which would be best for the fish.
<If you're growing them yourself, they're probably all reasonably safe.>
I intend to buy wet-frozen krill as another food for the goby.
Do you think that the eel would also eat those?
<Yes; spiny eels are hesitant feeders, and nocturnal to boot, but they
aren't over-fussy. My specimens have happily taken chunks of prawn, for
I also know that any and all molly fry will probably end up knight goby
What other foods would be good for one or both of them?
Some of the things I commonly see suggested, such as lobster eggs,
aren't available in my area as far as I know,
<Do try stores aimed at marine aquarists.>
and others, like tilapia, I don't think my parents would approve of
buying seafood sold for human use to feed to pets.
<So far as seafood goes, one approach is to buy white fish or squid for
yourself, and wrap the scraps in some aluminium foil and place it in the
freezer. Your fish aren't fussy, and for a few weeks at least such
scraps will contain sufficient useful nutrition.>
If I do get the Chromides, I plan on using one or two brands of cichlid
pellet or flake food for a staple, in addition to the smaller varieties
Finally, for the mollies I'll provide some sort of spirula-based flake
food, and maybe algae tablets, but I'd also like to give them fresh
veggies. When I see stuff like this mentioned, I always hear that you
should blanch the vegetables and put them in the tank when they've
cooled off, but I never see any recommendation for how long to cook the
Is there some sort of good rule of thumb for that?
<None. The blanching thing is about softening, not cooking. Zapping
lettuce in the microwave for a few seconds usually does the trick. But
lettuce is nutrient poor and shouldn't be anything more than a "salad
bar" that goes
along with the main course, i.e., the good quality flake. Some foods,
like cucumber, can be left in the tank to soften naturally, and the fish
will peck away at over time. Since these foods contain near-zero
protein, their impact on water quality is minimal, even if they end up
as horrible mush.>
Thanks for the help.
<Welcome. Sounds a nice tank and well planned! Cheers, Neale.>
Substrate sand....small brackish - 12/02/2012
One more quick question before I disappear again for a while.....
I plan to put the two baby 1/4" balloon mollies into a true brackish
I will acclimate them gradually of course.
<No need. Assuming specific gravity is going from freshwater (SG 1.000)
to low salinity brackish (SG 1.002-1.003, ample for Mollies) then you
can literally dump them into the tank!>
(They were kept with aquarium salt before I knew better. I plan to use
the marine blend salt this time, and I'll use the meter to check the
salinity.) I decided to do the brackish in a smaller tank that I have,
and then I'll restock the 29 gallon with another type of fish to start
out.... I'll probably choose the simplest kind of fish for the 29 gallon
this time around.
I'm interested in using sand in the brackish tank. I read your article
on WetWebMedia on substrate, and I also read this other article that
gets a little more in detail on the handling of sand substrate on a
I like the idea of sand for the look, and it's nice for the small shrimp
that will be the 2 baby mollies' only tank mates in the smaller tank.
Black sand seems cool.
<Can be; shop carefully though. If you plan on adding any digging fish
(say, gobies) then some "sharp" black sands, like Tahitian Moon Sand,
aren't ideal. On the other hand, midwater fish and shrimps will be fine
with whatever black sand you choose.>
Fish tend to like a dark substrate and it's attractive. Though, I also
like the idea of coral sand that you mentioned in your article which is
excellent for buffering. White also sparkles nicely.
<But yes, with freshwater fish, the colours fade a bit. Not an issue
with Mollies since the colours are hard-wired into them, but it's
noticeable how (some) cichlids for example "fade" in tanks with a white
substrate. Not all by any means, but some species.>
Either color works for me. (I just don't have undergravel filter
like you suggest though, I use a regular submersed one. So it
could work out differently I suppose….) (Would coral sand be too bright
for mollies and shrimp, would it be likely to stress out my fish?)
<Will be fine. For one thing, the sand de-colours with age, becoming
more off-white, even greenish.>
Also, the that stuff this guy in the cichlid article mentions about
gasses building up worries me a little, I don't know..... !
You have to disturb it periodically. As I'm a beginner, I don't
want to mess up the tank's chemistry accidentally! Sounds like he
is not afraid of it though.
<Quite so. The "deadly gas in the sand" idea is mostly a myth. It's
theoretically possible if you have, say, 8 cm/3 inches of sand. But if
all you're doing is adding enough sand to cover the glass, then gas
isn't likely to accumulate to any great degree. Even where deep sand
beds *are* used, this deadly gas problem just doesn't seem to happen,
and in fact, there are positive benefits to deep sand beds!>
SO, my questions for you regarding a proper substrate are:
1) would mixing a little coral sand with fine gravel like you suggest
avoid a buildup of gasses that using a straight coral sand for substrate
might incur? Maybe this is the simplest approach that would give
me some sandy look, but be lower maintenance than a thick sand bed that
tends to compact in the absence of burrowing species?
<Personally, I'd go with 2.5 cm/1 inch of sand, maybe with some coral
sand stirred in if you want. Easy to clean and risk-free.>
Or--2) would using a bare minimum of coral sand, or even just the black
sand, and just using it in a thin layer (perhaps 1/2 inch) and then
stirring it a bit weekly, help to avoid a gas buildup under the sand?
My main concern with sand substrate is if I accidentally allowed too
much gas to accumulate and then the fish become ill or die.
<Just doesn't seem to happen. The deadly gas is hydrogen sulphide, but
in practise, this gas becomes oxidised so readily when it emerges from
the sand that it's hard to get enough in the water to stress fish. Look
at ponds; they have thick, anoxic mud, yet the fish are fine.>
It sounds like the trick to vacuuming sand is to stay a half inch
above....maybe I could disturb the sand all around, and then wait till
it settled and do the vacuuming about an hour later to catch excess
debris I stirred up? Or is there some important reason that the
article I read says you should wait 8 weeks in between disturbing the
<I have no idea. I don't bother. I put the sand in and leave it there.
But I do tend to use snails and/or plants to keep the substrate
Those are just guesses of mine, but you know the actual science...I feel
that possibly using sand sparingly with regular agitation might be a
lower maintenance and safe way for a beginner to work with sand, but I
don't truly know. With gardening I've always strived to take the easiest
approach. Perhaps that really IS just plain old gravel in fish
<Can be. But sand has definite plusses.>
But if there's a way for a beginner to keep sand without a lot of
trouble, I'd like to try it in my smaller brackish setup.
<Hmm… do read more on substrates, here:
Re: Substrate sand....small brackish - 12/02/2012
Thanks, this is very helpful.
Have a nice week and happy holidays too.
<You too, Neale.>
BW Substrate Questions 5/5/07
Thanks for the help again. <No problem!> I have gotten a root
from PetSmart today and it looks great. I am going to go with the
crushed coral to help buffer the PH and also I like the
bright colors of my GSP. That is when I realized I had a couple more
questions. The first is: how to I calculate how much of the crushed
coral I will need in lbs? My aquarium is 30long x 12 deep x 18 tall.
<About 1lb/gallon.> The second is: I bought a few plants online
and noticed they have a ceramic base to them, are they ok to use in the
tank. <Shouldn't be a problem.> My last question is: When I
change to the crushed coral should I leave some of the old gravel
underneath? <I wouldn't. Change it all out.> Once
again thank you all, I get tons of info for myself and for my
daughter's freshwater and I always recommend you all to anyone I
run into that needs some help. Thanks again and keep up the great work.
<Glad we're so much help to you & your
Old Florida Crushed Coral Safe For Brackish
Tank? 2/14/07 Hello, <Hi Tom, Pufferpunk here> I
love your site! Could you tell me if it is alright to use Florida
crushed coral (the bags are about 20 years old, from a saltwater system
I was going to do that long ago, and didn't)? It is white, not like
the yellowish substrate they sell now. <I don't see why not, as
long as it hasn't been used before. Make sure you rinse
it well, to avoid too much clouding of the tank.> I'm planning
to have 1 mudskipper and 2 or 3 small mangrove seedlings I have (I have
a bunch of seedlings I grow in pots around the house in fresh water) in
a 20 gallon aquarium. <Make sure that tank is a 20 long, not a 20
high. A 30g would be even better. Try for one of
the smaller species of mudskippers. I always worry about a
skipper climbing up the mangroves to the outside.> Would you suggest
just rocks to build up a beach effect for the fish or what? <Rocks
are fine.> I have a few flat rocks that look like red
sandstone (or at least they are dark red and heavy) and one that looks
like something out of a King Kong movie (the rock formation he dreams
of. :-) Do you think these are safe for a brackish system? I tried
splashing plain vinegar on them and didn't see any bubbles
(remembered from Earth Science days in High School a million years
ago). <Sounds OK to me.> What would be some alternatives? Thanks
for your time and again I love your site! <If you wanted to set it
up for biological filtration, find something to hold gravel back behind
the rockwork & bury a powerhead with a prefilter attached under
crushed coral/gravel, making a waterfall from the
output. This looks great but would need to be torn down
& cleaned every 4-6 months. The larger the tank, the
less poop will clog this system. This is the powerhead I was
thinking of: http://www.bigalsonline.com/BigAlsUS/ctl3684/cp18554/si1382178/cl0/marinelandpowerhead660r ~PP>