Fish Aquarium?

Since your tank is still somewhat new you are going through a cycle. If you don't test your water to make sure you don't have high ammonia and nitrite during this time you can lose a lot of fish. The brown spots are probably just brown algae, if it bothers you just wipe it off.

Well - if you have kept aquariums for as long as you say then you probably have a water testing kit yes? If not - get the Freshwater Master Test Kit from API (Aquarium Pharmaceuticals). It's the best liquid testing kit on the market for testing Ammonia, Nitrites, Nitrates, pH, and they even have kH and gH testing kits.

It sounds to me like you do not have a completed initial cycle in your tank. 3 weeks is not enough time usually for this to have completed if what you did was a fishy or fishin cycle. I'd recommend doing a fishless cycle instead so you don't have to experience fishy deaths. Here's an article for you on that...

Fishless Cycling

http://www.tropicalfishcentre.co.uk/Fishlesscycle....

The brown spots that you are seeing on your tank are Diatoms. It's a living organism (not Algae), and not at all harmful to your tank or fish. It's a sign of the tank beginning to mature. There are various kinds of freshwater snails that will eat it up, or even a common plec will do the job (though they will do the job only because they probably are covered with Algae that is not visible to you). Otherwise - plecs don't normally eat the Diatom in the tank.

Good luck to you, and hope all this helps.

the brown spots are algae your probably experiencing a ammonia problem were the waste of the fish is not properly getting cleaned that can lead to restriction to the fishes air supply which could kill them to check for ammonia you can get test kits from your local fish shop

When you set up a new tank it takes 4-6 weeks for the biofilter bacteria to get up to speed to keep the water from getting toxic. How difficult that is to pull off depends on stocking levels and your pH. here's an article on cycling:

http://thegab.org/Articles/WaterQualityCycling.htm...

I'd get water tests for ammoina, nitrIte and pH and test your water to see if it's getting toxic. partial water changes and Prime would help dilute and detox ammonia and nitrIte.

That sounds like brown algae to me. fairly common in new tanks. Ramshorn snails or bristlenose plecos should make short work of keeping that under control. I wouldn't add any more fish till your sure your biofilter bacteria are up to speed.

The brown spots could be algae? I don't know. Did you cycle the tank before putting the fish in? Usually it takes about a month to cycle.

You just need to start a little slower and cycle your tank

also focus on a few live bearers and bottom feeders once your tank is cycled

check your nitrit levels, amonia levels, heck check all of them! Then call a fish store to see what you can do to bring the levels up/down.

it sounds like you haven't got a good ecosystem going. you need to get more good bacteria going in order to bring down nitrate and ammonia levels. Buy some "Cycle" or "Stress Zyme" to cycle the tank. good luck.

Have you put any ick medicine or anything of that sort in there i am thinking that ut us alerge. you may have boughten sick fish the water they came with may have been contaminated. you should prolly put new water in.

i say just by new ones and clean out fish tank