Newbie Advice Needed

[zugwang]

I got my first tank 3 months ago and am thinking of getting a larger one. I've made quite a few mistakes with this first one, just wondering how to avoid similar problems in the future. Some of the problems I've already had are:

pH drop, I generally check my pH every few days just to make sure it is ok. One time I noticed a significant drop in pH, what would have caused this?

yellowish coloured water. Could this have been caused by eucalypt leaves that were in my gravel? (I didn't know about washing gravel before putting it into the tank)

Dead fish. I've lost quite a few fish; two died within a few hours of putting them into the tank, 3 smaller fish just dissapeared completely, a kuhli loach jumped out while I wasn't at home and finally 2 mollies, 1 giant danio and an archer fish were fin nipped to death by a purple spotted gudgeon. What could I have done to avoid these problems? (besides not listening to the LFS who said the gudgeon was peaceful and wouldn't attack anything)

At the moment I have an 85 litre tank with:
2 khuli loaches
2 dwarf gouramis
2 panchaxs
1 bristle nose catfish
1 black ghost knife fish (it was a present, I know it is too big for my current tank)
2 siamese flying foxes
1 black lancer catfish

I'm thinking of getting a 150 litre tank (maybe a little larger). What should I know about setting up the new tank, should I put the more timid fish in first or put them all in together?

What other kinds of substrates are there besides gravel? I've heard of peat moss and sand, anything else?

Plants, what kind are there and what should I put in?

More fish, would I be able to put more fish in the larger or do I have enough already? If I can put more fish in what kinds? (I live in Australia and we have funny quarantine laws so not all species are available here) I also want to avoid aggressive species (the gudgeon I had caused enough damage)

And finally anything else I should know?

 

[dwarfgourami]

If fish die within a few hours of being added to the tank, I would suspect that there was a big difference in water parameters between the shop tank and yours, and that maybe you did not acclimatise them carefully enough. Other that or they were already ill with something really serious. OR that the water stats were really bad in your tank and the new fish just couldn't take it.

How did you cycle the tank? Several of those fish are sensitive and should really only go in a mature tank.

What are your water stats (ammonia, nitrites, nitrates)?

How much reading up did you do on the respective species before you bought them? It is really easy to google fish these days and get the information you need on their maximum size, need for space or hiding places, feeding needs, whether they are territorial or need to be in shoals. For instance, a giant danio needs to be in shoals (and in a MUCH larger tank than a 85 ltrs).

The tank is quite clearly overstocked. I have no personal experience of either black ghost knife or lancer catfish but am prepared to bet that a 150 ltrs will also be too small for a BGK anyway. (Please comment on this, folks!).

Are both your dwarf gouramis males? That could lead to nasty territorial problems?

Check out the thread on Your 5 top tips above; there's some good suggestions in there.