Nitrate Sponges,

[nessar]

So any ideas about whether the nitrate sponges absorb anything other than nitrate?

Or what else I can do to lower it? I have plants, but only my straight vallis seems to be growing. Any reccommendations for fast growing, low light tolerant species (dont think my bulb is much good for plants, had quite a few die).

 

[Curiosity101]

So any ideas about whether the nitrate sponges absorb anything other than nitrate?

Or what else I can do to lower it? I have plants, but only my straight vallis seems to be growing. Any reccommendations for fast growing, low light tolerant species (dont think my bulb is much good for plants, had quite a few die).

Elodea (plant) and water changes would be my best advice. Have you actually tested your tap water? 25-50ppm seems a bit ambiguous but maybe it fluctuates?

Fishwise, if there are any you'd happily part with for the sake of the others then advertise free on here and aquarist-classifieds. I assure you someone will want them. If they're all fully grown and you're seeing no ammonia + nitrites then your filter is coping fine (as bignose said) but you do want the filter to do between 5-10x the volume of the tank per hour (again as bignose said). Basically a bare tank would probabaly be fine with 5x and a heavily planted/decorated would need more like 10x.

As for yellow water - do you have anything that could be leaching tannins? If so take it out and boil it for a bit or get some activated carbon chips (they come in a big box for like £2) and put some in a small nylon net (like the type used for laundry tablets, or fishnet tights) and put that somewhere around the filter inlet/outlet. If it's tannins then this'll clear them up. You will need to refresh the carbon every now n then (when the water starts going yellow again) until all tannins have been released and then soaked up by the carbon.

N finally, are you actually encountering problems with your fish or do you just want to lower your nitrates as a matter of course?

 

[nessar]

Well my test kit isnt very detailed, it goes 25, 50, 100, 200 with measuring nitrates. So the reading from the tap water is somewhere between 25ppm and 50, whereas after a week the tank water is between 50 and 100.

No, no problems with the fish really, its just some people say 25ppm nitrates is bad, whereas others say up to 200 is okay. And water changes every 4 days kills my back. Have had 2 gouramis die though, 1 dwarf and 1 honey, for apparently no reason, since I set the tank up.

Filter can do 300 lph apparently, has always coped with bioload fine, never seen ammonia or nitrites after the fishless cycle. Have a sponge filter in there too atm, but thats only temporary. I have driftwood, a coconut cave, squibwards house, a bamboo plant, straight vallis, 2 i cant remember the name of but they are smallish, and 5 small moss balls - thats the decoration.

There are drifwood and homemade coconut caves in there, but both have been in since mid march. I've always had the yellowy water issue, but I think its just been more noticable since I got sand a month ago. The driftwood leached tannins loads to start with, but surely this would have stopped by now?

 

[Curiosity101]

Ahh... do you have a paper strip test kit? I really would bin that, they're really inaccurate... Until you get a definite reading on the tap water it's hard to say what your tank should be at, rough rule of thumb is around 20ppm above the tap water when it comes to the weekly water change.
You may be able to get a rough estimate of your water from your water suppliers website. eg. I'm from sheffield and my supplier is yorkshire water. I can go on their site, click water quality and then put my post code in for the results of the water in my area.

I personally would have a more powerful filter, but whilever it's fine with your stock and keeping the water oxygenated then there is no need to change it.

And yes the wood definitely could still be leaching. Put it this way have you always had stuff that could be leaching in the tank? If you have then it's almost definitely tannins.