High Nitrate

If your nitrate is going up so much during the week between water changes, something is making that nitrate. The usual causes are :
Too many fish - but this doesn't apply in your case
Feeding the fish too much as the left over food decomposes to ammonia which the bacteria turn into nitrate
Not enough or large enough water changes - you do yours weekly, and 40% is a fair amount, though the increase is substantial between water changes. It is usually recommended to do 50% or more nowadays.

If you deep clean the substrate, it isn't 'stuff' trapped in there. Which leaves the filters. How often do you clean them? The brown goo that collects on the media is left over food, fish poo, bits of dead plant etc and the goo is often referred to as a nitrate factory. The filters should be cleaned every couple of week - as you have two, clean one every week, alternating them.

Floating plants do take up a lot of ammonia that would otherwise be turned into nitrate, you could try those rather than plants that are rooted in the substrate. Anything from duckweed to water sprite, via Salvinia, water lettuce, and Amazon frogbit. Floating plants do not seem to suffer from algae, though if your water is soft you would need to add a trace mineral fertiliser.


This doesn't solve the problem of the tap water nitrate though. A lot of people with high nitrate use a Pozzani filter to prefilter the water for a water change.
Other members with high nitrate will have other suggestions to add.

What substrate do you have? If gravel are you gravel vaccing to remove built up wastes?

Hi there. 

My tap water has a nitrate level of 40ppm, so my sympathies are with you here. I use a tap water/RO mix on some of my tanks, but not all of them (way too many). I'm currently looking onto ways to reduce my nitrate levels, and have bought some of the Seachem media. I'm under the impression that this won't have any impact on your levels immediately because the nitrate is used by anaerobic bacteria, which could take a while to build up to useful levels.
Substrate in my tanks is sand over planting substrate, with live plants, and although my tap water has high nitrates, I don't get any increase between the weekly water changes.
I also have plecs, and adorable as they are, they are also very messy.

I have some suggestions, and it would be useful to see what the others think before you consider taking on any of them.

To deal with the current algae problem I would consider blacking out the tank for several days. Blocking out all light should cause the algae start dying off.
At the same time I would start to do daily siphoning of waste, and try to scrape as much algae off decor as possible. Maintain weekly water changes & alternating filter cleans.
I would also consider removing the gravel. Not only because waste sits on top of a sand substrate, so it's easier to see to clean, but I've previously struggled to keep gravel clean if there is anything else underneath. That may have been more about my abilities (or lack of), but I found it difficult to keep the gravel clean enough, without removing the sand underneath whilst siphoning.
Once the algae has been dealt with (hopefully within a week or two), then floating plants would be useful when the lights are back on.

Dealing with tap water nitrite levels is a more long term issue, but at least we should be able to get to a point where your levels are not going up between water changes fairly quickly.

Would you be able to post some pictures of your tank, and provide as much information as possible about it (lighting periods, location - does it get any direct light, etc), and we'll see if we can make any more suggestions to resolve you issue.