elmo666 said:
Good points lunar jetman. As I said I was quoting an article giving guidelines, and with less than 180cm of fish, I'm comfortable that my stocking is low, certainly not heavy. I have been able to see the level drop back after a water change, but doesn't stay there for long. I use the API master kit, and you're right, very difficult to differentiate between the 2 higher levels, which makes life difficult because one is double the other!. The plants are fed, but its nitrate free, only micro and macro elements. I wouldn't claim to have a spotless tank, no chance in a fully planted set up, but I do manage to keep a lid on it so to speak. Another confusion is the lack of any type of visible algae, which I would expect in a high light/nitrate environment. Hope none of this comes over as argumentative, as I said appreciate all the replies, just frustrated how quickly the levels rise. If anyone has had the same problems as me I'd love to hear. Incidentally, the set up has been running trouble free, putting aside this recent nitrate issue, for 15 months. No disease, lost one ram 6 months ago, and plants thriving, need thinning out monthly.
Firstly, no this doesn't come over as argumentative. You're trying to work out what is going on in your tank and we're all trying to help by offering advice and guidance from our own experiences. I'll take your comments in good spirit if you do the same for mine!
Taking your comments in order, I found the article I think you were referring to in relation to stocking volumes and I have to say that its all down to a matter of opinion but its dangerous to just say 1cm per litre. You're saying that you think you can put nearly 4 metres of fish in your tank, or at least 3.75 metres. I would strongly disagree with that statement. You can't just arbitrarily add 60% to the capacity because you have an external filter for example. Your external filter may not be as powerful as the next persons internal filter and I've never thought that by having an external filter rated for my sized tank (which I do) means that I can have a greater number of fish as opposed to having an internal filter rated to my size of tank. (which I have had in the past)
I've just used the calculator for surface area and got a figure of 160cm for my tank (which is 288 litres, 120x40x50cm) but the volume and filtration calculator says I can have 461cm of fish. That's 3 metres difference between the two figures! I couldn't get over 4 and a half metres of fish in my tank!
Add to that, you have to take each type of fish on its own merit as some fish need more space than others, e.g. Clown Loaches individually will get to 15-20cm if not bigger and need a minimum of a 4 foot/75 gallon tank, preferably bigger. You have four so you could have nearly a metre's worth of fish there when fully grown.
What you should be doing is using the fully grown size of a fish to determine if its suitable for your tank and not its current size, e.g. you could put both a shoal of 5 neons and a couple of young clown loaches (say 5cm each) in a 2ft tank initially, but whilst the neons might be ok there permanently, the loaches would quickly outgrow the size of the tank. (and probably not he happy in that low number and small tank as they like to swim, but you get my point)
Therefore, in my opinion you should have around 120cm of fish in your tank and you currently have 179cm (a figure that will likely increase as the fish grow)
I'd also wager that your macro/micro fertilisers have some nitrate based chemicals in them otherwise they're unlikely to be giving your plants the nutrients they need. E.g. mine has potassium nitrate in it and results in higher nitrate levels. I suggest you have a look at
this site which has chemicals you can mix yourself to make micro/macro solutions, Also you can look at
this site's calculator which gives advice on what you might need to mix yourself.
Also, if your plants are thriving under the lighting/nutrient levels you have, its likely that you won't have algae but you could have elevated levels of nitrates.
How often do you change the water? I would expect (and hope) that you are changing around 50% every week, otherwise the volume of fish and plant nutrients will cause high levels of nitrates.
I presume you know all about the Estimative Index method around micro/macro that you're using?
James' Planted Tank gives a good description if you're not 100% clear.
In summary, I think you have a combination of a planted tank, high in nutrients (even higher if you don't keep up the water changes) and an excess volume of fish which is causing your high nitrate levels. I'm betting that 15 months ago all these fish were smaller or have been added over this time so what you're experiencing is a slow build up of nitrate levels, plus the regular doses of nutrients that increases them further.
I hope this helps.