Black Onyx sand


Lifetime Charter Member
Lifetime Member
Jul 7, 2006
OK question for Tom? You've mentioned using Black Onyx sand for natural aquariums. I don't know if it rings a bell but I'm the guy that intends to build a 2500gal concrete tank with 10' viewing window when we build our house. My research would indicate this is affordable for a middle class family if done on a budget. I intend to put about a foot of substrate in back and grade it down toward the front to 2". My fish list is as follows:

Fish Size Qt Total Tally
Red Cockatoo Cichlid 2.5 1 Pr 5” 5”
Apistogramma Viejita 3” 1 Pr 5” 10”
Flag Acara 3" 1 Pr 6" 16”
Ram Cichlid 3 ” 1 Pr 6” 22”
Keyhole Cichlid 4” 1 Pr 8” 30"
Silver Angelfish 5” 7 35” 65”
Banjo Catfish 4” 10 40” 105"
Panda Cory 2” 15 30” 135”
Coral Pencilfish 1.5 50 75” 205”
Black-Winged Hatchetfish 1.5” 200 300” 505”
Otto 2” 200 400” 905”
Cardinal Tetra 2” 300 600 1505”
Rummynose Tetra 2” 300 600” 2105”
Green Fire Tetra 2” 300 600” 2755”
Brazilian Yellow-Belly 1.5” 100 150” 2855”
Grass Shrimp

The design of the tank is something like this:

Can I use Black Onyx sand exclusively? And when you say sand you mean the sand not the gravel.


Lifetime Charter Member
Lifetime Member
Jul 7, 2006
I had to rush off to the dentist so I couldn't finish. I'm also wondering in your experience with large tanks. Will the Tetra's form seperate schools or will they all just lump together? If they're just going to lump together maybe I'm better off with just one type of tetra? I curently have Rummies (with the Angels) in my 180.

Tom Barr

Staff member
Jan 23, 2005
Generally they will form their own schools, but they will merge here and there.

The pencils tend to stay to themselves, as do the Rummy(anything their own size like the ottos will school with them as they pass by.) and cards, and Hatchets, Apistos obviously do.
I would not put the Acara/Keyhole in there.
Banjo cats will eat the shrimp as will the Angels.

Ottos will swim with the Rummy's.

I'd look for some alternative fish.
Sturisoma are large, neat and will not go after small fish.
N esepi stay to themsleves.

By sticking to relatively small fish, the tank will look larger than it is.
Your chances of fry making it to adulthood also go way up.

Think long term for the fish.
Also think about how you plan on removing them if you change your mine:)
In other words, take a long time and use the other tanks to judge and see.

I like larger rare plecos, they do not eat (most) shrimps or other fish, but come out only at night etc, rather than appearing in the day.
Nuggets, gold spot, mango, even the large A. adonis work well.
the smaller plecos all can be used, the larger spiny ones(other than A adonis) , and Panaques etc should be avoided as well as the Vampires.

That makes the tank look larger but still allows me to have large fish.
The Sturisoma hang out in the day some they are nice and get 12" long etc.

I'd suggest you stop worrying about adding these larger fish.
Add large schools, that has a much more dramatic impact.
folks think they must have a central theme fish that's bigger than the others.
Try your best to get away from that. It'll free things up for you and allow more choices and a better overall look.

Bleeding hearts, Serpae tetras, some of the smaller brown knife are well suited,
Hemiodopsis are very nice in large numbers.They make a nice alternative to Rummy noses.
If you could ever find Synaptolaemus , that would be awesome to have 100-200 of them!

Panda Corys are about the nicest in large schools IMO.
I like the Barbatus, sterbai and aldolfi and have had them all in large tanks, but over all, the pands still appear nicer for such displays.

Try gluing Cork bark to the sides of the tank. It's pretty cheap and makes the tank look very nice. Make as many levels up towards the back as you can.
Larger => small as you move towards the rear, this will make it look deeper than it really is.

It fools the eye by making it appear farther away and gives better depth perception.

I have two personal larger tanks in the works.
A 180(agressive) and 225 gallon(community).
Both are South American.
By helping other folks, doing client tanks, I've really changed my own ideas and layouts.

I think a pack of Hemiodopsis(there are a few species to pick from) would make a nice display and very fast and active. I also think the schooling will be more distinct with them as well. Some of the other suggestions will still allow larger fish, but since they are more cryptic and stay on the surfaces, they do not detract from the display.

Do not spend 1 year planning and getting everything justr right, then rush a fish choice or add a fish just because you want to fit them in the tank.
That's a bad habit many do.

Tom Barr


Lifetime Charter Member
Lifetime Member
Jul 7, 2006
Tom, Thanks for the reply. The Angels are a must. No problem getting rid of the Keyhole and Acara but my curiosity is peaked: why get rid of them? Also what do you think of Onyx sand as a substrate for this aquarium?

"If you could ever find Synaptolaemus , that would be awesome to have 100-200 of them!" I can't even find what they are never mind find them for sale. What are they?