Nitrate levels at 160ppm+ and this guy still says it's alright???!!!

The tank's lack of water changing is definately a large factor in its poor health. However, without knowing more details about this tank, I would also suspect overcrowding and perhaps overfeeding as well. One time, I had to leave on holiday for 3 weeks, and left my fish on an automatic feeder. My nitrates were higher than usual (I don't remember the reading), but definately not as high as 160ppm+.

You are correct in assuming that the nitrification process is eating away at the buffering capacity of the tank, thus leading to the bottoming out of the pH of the tank. Medication will not fix the tank, though it may help fix some of the side effects. The only way to permanently fix the tank is to slowly build up the buffering capacity of the tank through water changes.

Tell your boss, for half the price which these guys are charging, you'll do the tank maintanence for him. With the proper equipement, 40-50% water changes once a week for the average sized tank won't take up too much time, and in the long run it'll be much better for the tank... your boss will be happy, you'll be making some extra cash on the side, and you'll get on your boss' good side (always a good thing). If you do manage to convince your boss that weekly water changes is a good idea, I'd suggest starting slowly... 10-20% water changes once a week. Over the course of a few months, work your way up to 40-50% water changes. The tank water is probably quite different from the tap water, so caution should be used. Keep monitoring the water and things should turn out for the better.

-Richer

Nitrates under 40 ppm are good; under 20 ppm is better. That assumes your water starts out at zero nitrates, of course.

Nitrates in an of themselves probably don't pose many short-term dangers to fish, but over the long term that may not be true. Also, if nitrates are that high in the tank, there are probably lots of other dangerous compounds that are reaching toxic levels, too.

I'd start changing water, about 10-20% at a time, every couple days, until nitrates drop substantially. Another danger with neglected tanks like this is the acidification of the water from normal biological processes can cause pH to drop very low. This either slows or kills the beneficial bacteria that make up the biofilter. As you institute water changes, the pH may rise. This can 'wake up' the biofilter bacteria, but often not as fast as it causes ammonia (non-toxic at lower pH) to become toxic as pH rises. For this reason, you really need to be testing pH, ammonia and nitrtites as you start changing water.

It may be that your tank will completely recycle. If not already familiar with cycling, a quick read of some of the 'sticky' cycling threads can be helpful.

Good luck,
Jim

Who does the feeding, the boss or auto-feeders? It is not easy to get to 160ppm with massive overfeeding, overcrowding, or both. If it is the boss, stay out of it. It is not good practice to tell the boss he does not know what he is doing.

Select your battles. This is one best not fought IMHO.

my boss has a contract with this company for 2 years so there's a still 1 year 3 months left!

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For the past 9 months fishes has been dropping like flies

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Can you see the contract? What clauses does it have for liability and termination and stuff? I'm sure your boss did not contract for a tank of dead floating fish... if he is noticing this then he would agree with your facts (if properly presented, i.e., dead fish, glowing radioactive unchanged water) and terminate the contract under whatever provisions are there, and you could take over your own 300g tank. Or you could threaten the contractor with termination unless he start more frequent water changes... might work.

These people Are annoying the best way to fix this would be for YOU to start taking care of the fishtank..people just wont listen..ergh

I think most fish can take nitrate levels up to 80 ppm but this is probably pushing the limits. Trying to keep them under 20 is your best bet.

What is the pH of the water going into the tank.

My tap water has a pH of 7.4. I thought small weekly water chnages was going to be good but I assume a combination of small water changes and plants quickly ate my small buffer as it would drop to pH of 6 after a couple of months. Now I do bigger changes (20%).

Does the company that maintains the tank replace the dead fish at their own expense?

If they do, I would love to be in your position. I'd be taking a fish home every week.

Doesn't hurt your boss and that company obviously doesn't mind losing their fish.

Do they have a set combination and number of fish of each kind on their tanks? Do you remove and dispose of the fish corpses yourself or what?

I'm curious about how they handle replacement and maintenance of the numbers of the fish in the tank.

Hell, tell your boss and he can start selling a fish here and there to people. Recoup some of the expense.