Slowly Rising Nitrate Levels

[mbpted]

After several bad starts I think I have a great tank. Fish are all happy and healthy (as far as I can tell) and the water tests have been good. Stable and with good readings.
 
I do a 50% water change every week, and the water is clear.
 
The light is on a timer and the light clicks on in the morning and clicks off at night. (it's on about 12 hours a day)
 
The tank is in a room that gets sunlight, but the windows are curtained and no direct daylight hits the tank.
 
Water readings are:
 
pH: 7.8
Ammonia: 0 ppm
Nitrite: 0 ppm
Nitrate? Ah here's where things are changing.
 
When I was restocking and gradually adding fish (the last new fish were added about 2 months ago) the Nitrates were at 0 ppm, two weeks ago they climbed to 5 ppm. This morning I tested again and they had climbed to 10 ppm. (I test about twice a week)
 
Is this normal? Is it getting too high? If so, what should I do to reduce it.
 
Although the water is clear, the glass is starting to get some green/brown stains on it. I clean it when I change the tank but they are coming back more and more. I have no live plants in the tank.
 
The last fish I added were two Marbled Mollies. (as I said, 2 months ago) When I first added them, they took a while to get used to feeding time and where and how to get to the food. (floating at the top of the tank, where the others - 5 danios and 3 serpae tetras - go at it in a frenzy) While the Mollies swam around oblivious of the flakes and blood worms I would drop in the tank, I noticed them nipping at the rocks and fake plants around the tank. I think they were eating the algae.
 
Since then, they've figured out how to get to the food with the rest, and I don't see them picking at the rocks any more. 
 
Is the increas in Nitrates due to the appearance of the algea on the glass? (I'm assuming it's algae)
 
My tank is only 10 gals. I think I'm at my limit of adding new fish, so I'd be nervous adding anything that would be specific to eating algae. (a pleco or similar cat fish)
 
I haven't had too much luck with snails. The last Zebra I added only lasted a couple of weeks before it died. I tried to wait to see if it would perk up - smelling it daily to see if it was still alive, when I finally got the dead snail smell, I think it poluted the water. My pH and ammonia shot up, the fish were beset with fin-rot and it took several weeks and a dead serpae to get things back to what I felt was comfortable and stable. A couple months later I added the Mollies.
 
But that was then. Almost half a year ago. I think my tank was still cycling, and I added him along with the 5 Danios. That's probably too many fish to add at a single go, but I wanted them to school and calm the Serpaes that were nipping at each other. (a suggestion from the girl at the local fish store - which worked!) But it did mean a spike in ammonia and I had to change the water in the tank quite frequently. The snail was active at first, moving all over the tank, the walls rocks, etc. Then it just stopped, sat in the corner and didn't move again.
 
Anyway, Should I be worried about the increase in Nitrates? Should I add something to help get the green/brown algae off the glass. (and what?) Should I clean the glass and change the water more often?
 
Hope I didn't write a novel, I wanted to be thorough with my descriptions in case it would help with suggestions.
 
Any help would be appreciated.
Thanks.
 
 

 

[Colonel Dibble]

Hmm, not an expert at this sort of thing, however, from what I know...
 
1. Add Plants, they will fight off algae and keep your nitrates down, as they take nitrates out of the water.
2. You may be over-stocked which is why your Nitrates are on the incline. 
3. You might not have good enough filtration for a tank of your size.
4. Do not add Catfish. They will only increase the amount of Nitrate in your water as they produce more waste than they can get rid of algae.
5. Have you tried Ramshorn Snails? They are small, barely produce any waste and will give the algae a good go.
 
Water changes reduce the amount of algae in your tank and also wiping the algae off the glass with a cloth is what I used to do. Don't let it build up if you can help it.
 
Hope you found this helpful.

Edit: Apparently 50ppm Nitrate is when you should start to worry. Don't let it get that high though, wait... you don't have plants in there? If you don't you should try and keep the lights on a bit less. the more your lights are on the more algae will appear. I recommend either getting lights that won't produce as much algae: such as some LED lights. If not then reduce the amount of time the lights are on, and let some natural light in, when you can. (not direct sunlight obviously)

 

[fluttermoth]

I think your main problems are; your lights are on for too long, that's what's causing the algae (or at least some of it). Cut the light back to six or eight hours a day see if that helps.

It's natural for nitrate to go up; it's the end product of your nitrogen cycle and one of the reasons for doing water changes. Try not to let it get higher than 20ppm more than the level in your tap water

 

[mbpted]

Thanks for the responses. I'll cut back the light to see if that helps, and look into adding a live plant. I'll also do some research on Ramshorn Snails.