pocosumus/any other fish

Question
My pocosumus has a white spot on the back of his head. I think it is due to him sitting/sucking right behind the heater and it burned him. What do I do to fix that? If I can.
Another question is I have had my tank for about 3 weeks now and it doesn't matter what kind of fish I put in there I kill them. My PH is fine..the amonia is fine. I don't know what to do to be able to keep fish...I hate killing them all the time.Please help. This is my first fish tank and I have read everything I can on starting a new tank but it isnt helping.

Answer
Good evening Mellanie, thank you for your question.

Your plecostomus (that is the correct spelling, by the way) is a hardy fish that will tolerate many beginner's mistakes. Don't worry, we've all been there! Don't give up. All you need is an understanding of what is actually going on...

Your tank is likely not entirely done cycling. Three weeks is usually about right, but there can be exceptions. Beneficial bacteria need to grow (on your filter media, your water, your gravel and your glass) before you can manage any sort of bioload in your tank. What are you using for a filter and filter media? I make sure my filters offer 3 way filtration - biological (growing the benficial bacteria), mechanical (the actual removal of particles and matter) and chemical (neutralizing the bad stuff in your tank).

Biological filtration is performed by using ceramic rings and sponges. Sponges actually perform biological AND mechanical filtration. I add a layer of filter floss (the white fluffy stuff in the fish department of say, Petsmart) which removes lots of particles from the water. I also add carbon, but instead of using regular activated carbon, I use Chemi-Pure. One 10 oz. bag lasts me about 3 months. Regular activated carbon only does its thing for a week or so, after which it only serves as a host to the beneficial bacteria.

I know this may sound complicated, but I believe you will have better success if you use a better filter. Look into the AquaClear line by Hagen. Here's a link for you:

http://www.wetwebmedia.com/ca/cav1i2/Equipment/filters.htm

Secondly, do you have some test kits? It sounds like you might, and you are probably using test strips. The liquid kind are preferable, because the strips are notorious for being inaccurate and dificult to read, but they should be giving you some notion of your water parameters. Ammonia is the first step in the nitrogen cycle. The beneficial bacteria (see above!) break it down into nitrite - which then gets broken down into nitrate, a less harmful substance. Your test kit should tell you all three readings. Ammonia and nitrites must always be at 0 ppm - always! Even half a point will cause your fish to succumb to ammonia poisoning. Gill burn, fin rot, redness in the skin, and above all gasping at the top for air, are among the signs.

So you see, your ammonia can't really be "fine" - it has to be undetectable! If you are detecting any, your tank's cycle isn't finished yet. Keep your pleco in the tank with no other tankmates for another couple of weeks or so. Leave the light on for only about 8 hours a day, if possible. Purchase some algae wafers (Omega One makes my favorite brand, although Hikari is fine) and feed your pleco one wafer at night just before you turn the lights off. You can also feed him fresh veggies. Cucumber and zucchini slices and romaine lettuce (clipped on with a magnetic clip so they will sink to the bottom) will supplement his wafer diet nicely.

Water changes tend to interfere with the cycling process, but you should still be changing 10% of the water every day if you are detecting nitrite or ammonia of any kind since you have a living creature in there. If your levels are 0 ppm, but you don't have any nitrate yet, your cycle is almost done but not quite finished! Change 20% of your water a week in this case. Use dechlorinated tap water. The water conditioner I use is Prime (Seachem) it removes chloramine - which is harder to remove than chlorine - and is used by many municipal water supplies. Prime can also help you bring down ammonia levels in case of an emergency. Pick some up!

Do you have a gravel vacuum? Do a gravel sweep to remove uneaten food and detritus from the gravel. Oh! Do make sure you don't overfeed - this will cause an ammonia spike for sure. One small pinch of flakes twice a day is all you need. All the food should be gone in just a couple of minutes.

When you feed frozen foods (and you should, since a flake only diet is nutritionally incomplete and awfully boring for your fish!) be sure to defrost them and drain them of the "juice" they're packed in, using a small strainer or slotted spoon. Brine shrimp enhanced with spirulina or vitamins, mysis shrimp, and bloodworms are all fine choices.

I hope this has helped. Honestly, I would not be too concerned about the white spot on your pleco if it is indeed a burn. I would just keep the water very clean. You might want to turn your heater sideways - horizontally, that is.

Good luck! Feel free to write back.
Nicole

P.S. I know you said you've read lots, but how about this? http://freshaquarium.about.com/od/aquariumstartup/Aquarium_Startup.htm