Stocking question for 20 long

[shmagu]

I have a 20 long that I was using as a community tank for Tetras and Corys. After reading and doing some research, I decided to switch to a Tang community and have a couple of questions. The tank was set up four days ago with pool filter sand, approximately 12 pounds of tufa rock on one side, a piece of driftwood as centerpiece and shells on the other side. I'm currently using a Penguin 170 Bio-Wheel and also have a 125 and a 100 that I could also put to use. Since the filter was already established, I let the aquarium sit for 24 hours and then added 5 Zebra Danios. I tested the water the same night I added the fish and it looks ok to me (8.2pH, 0 nitrite, 0 ammonia, 20 nitrate, 15KH, 30GH). I checked again 48 hours later and the only things that changed were KH dropped to 13 and GH dropped to 26. I'm not exactly sure I understand the difference between these two even though I do know where they should both be. Is it normal for these to drop like this and does it have any affect on the fish?

Also, I would like to add a pair of transcriptus and some brevis. When should I introduce these and should they be added at the same time? A more important question is exactly how many would be ideal for this setup?

[fishlips]

Your answer is cichlidforum.com you won't be disappointed.

[shmagu]

I've been looking around there, but still can't determine which of these, transcriptus or brevis, should be added first or if it's ok to add all of them at the same time. From what I see, it looks like 1m/2-3f of each would be alright for a tank this size with the 5 danios already there. I really need to know if I can add them all at the same time or one before the other.

[Jayhawk]

I'd add them at the same time if they're all young. Both brevis and J. transcriptus are PAIR bonding fish. Adding extra females at first will help ensure a pair forms, but when they pair up there is a good chance you'll need to remove the extra females. Personally, I always tried to start with 1 male and 3 females if I could afford it...

BTW - I had a 20 long set up with these two fishes, and it worked out fine. I'm not sure how well it would work if your transcriptus bred - mine never did, so I wasn't ever sure I truly had a pair or just two fish that got along OK. My brevis bred like mad though!

Eric