Backyard Aquaponics
A place to discuss aquaponics

if you have sand mixed evenly, it could lock off large sections of your GB. Beneficial sand creates small anoxic areas (I assume we're talking RSG here) which can be beneficial, but these could be concentrated low flow areas, not like the rest of the GB.
I'd definitely grade it.
Your GB should drain fast for oxygenation.
Don't forget to wash it after grading!!!

Actually, I am planning on washing it while grading. Setup a screen, dump a few shovel fulls on the screen and wash - the sand will drop leaving the rock. End result is clean / screened pockmarked peagravel.

Not sure by the way how I could achieve sand being mixed evenly - surely it would settle to the bottom fairly rapidly - especially in a country that tends to jiggle all the time from mini-earthquakes. We are always straightening pictures and things.

Yep CRT.. wash as you grade it.... even 1/4 inch is getting toward the smaller side for media as far as oxygenation/draining.... especially if you're "rocking" the system every now and then....

Being an ex-Kiwi, I can relate to the odd (about 1000/year) small tremor.

1/4 " will compact down over time anyway IMHO just with the flood and drain action... rocking it back and forth periodically will just compound that tendancy and fill small voids that would otherwise retain water/oxygen.

Get rid of the sand all together I'd suggest as otherwise I think you'd end up "sifting" it into an almost solid layer on the bottom of the growbed over time.....

From my experience trying to remove the scoria silt I allowed to set in my barrow after washing, I concur wholeheartedly Roz.
3 mini-Quakes per day? Really? Wow!

That's only counting those that you can feel Kuda....

Sesmic recorders actually record between 10,000 - 15,000 "quakes" annually somewhere along the 300+ active fault lines.....

We aren't that bad - I think we have felt about 3 to 4 in 3.5 years here. Nothing really bad either. Where we live is very stable - it isn't like other parts of Costa Rica. (Central Valley and the Pacific side)

Good to hear about the fish.

I was just responding to your initial post that stated the Pacu were hard to find and that there was not much known about raising cats in your area.

Sounds like fish won't be an issue after all.

Hi CRTD,
I am using 1/4" gravel and I didn't wash it because it was frozen at the time. I now have a good layer of sand and silt at the bottom of the beds, which may be why I am having issues with biofilter efficiency (nitrite keeps showing on tests). If I were to re-do it I would try to get as much out as possible, and I would try to make the drains work to remove the sand if it does reach the bottom.

Ah - Pacu are in the rivers, I will just have to spend some serious time fishing - I am trying to come up with a down side to this but so far I can't.

Raising cats is not well known, but that is what the internet is for...

Thanks for trying to help. Getting fish won't be an issue. One thing I ran across though is that Pacu might be pretty boney. I don't want boney.

I have not heard boney, I have heard meaty.

As for the Pacu caught in the rivers, I don't know how many you want, but so far I have found no one who has been able to breed them in captivity with out doing it manually. I would love to know if you are able to catch enough small Pacu to make it worth it. Would you be able to breed them manually if you caught the adults?

Hmmm, if they are meaty, I am interested.

If I find a bunch of them - I will just use the throw net and get a bunch of little ones. Shouldn't be hard. I can always walk down to the river and throw in the net and just filter out whatever I don't want. No reason to be too picky in reality.

I love the tropics.

From what I've read, Pacu is a delicacy. The flesh is tender, mild and slightly sweet, and not too bony. I'm speaking of what we call Pacu in America Piaractus brachypomum (Red-bellied Pacu) or Colossoma Macropomum (Black Pacu). I believe in South America those fish are called Tambaqui, Paco, Gamitana,Cachama, Cachama negra,boco,Morocoto, Ruelo, Cachama blanca, Caranha, Pirapitinga.

There are other fish called Pacu -- some we call Silver Dollars -- they don't get as big and are bonier but are farmed and fished as a food source.

I'm assuming you're fluent in Spanish, living where you do -- If you find any information on breeding either of the two species I mentioned above, I'd be interested. Aparently there are fairly large fish farms in Brazil, Colombia, and Peru that raise these two species. So most of their research is published in Spanish. I can read and understand enough Spanish to get directions and find a restroom, but not enough to read scientific literature and understand the nuances. I've read that getting Pacu to breed in captivity is difficult and they inject hormones to induce spawning. If there's another way, I'd like to find out and try it.

Yes, I am pretty good at reading Spanish and speaking it. No problem really. As I say, I can confuse people in three languages now.

When I start my search for fish - I will do some research on Pacu - yes, it is the first one you mentioned. A member of the Piranha family as you can tell from the name but mainly eats fruit. It is supposed to get rather large (5 kilos) and be a very good fighter.

The black Pacu (Colossoma Macropomum) supposedly get huge -- over 60lb. In fact some people call them "water pigs"