Jump to content

High nitrate - how often can I safely do water changes?


mouth

Recommended Posts

Hi everyone,

 

Let me start by saying that my wife and I are very amateur fish keepers. We have a 4'l x 18"w x 2'h tank stocked with a total of 21 assorted African Peacock cichlids (plus 2 catties). We don't know the official names but included are electric yellows, blue dolphins plus 3 or 4 other types. Filtration is by way of an Aqua One Nautilus 1400 canister filter and an internal filter operating at 1000lph. The water temperature is around 25deg c. We have had the tank operating for 3 years and had only lost 1 fish in this time. Until recently that is. I have been getting slack with water changes and filter cleans - sometimes getting out to 3 weeks between cycles, I know this is not good and we have paid the price for this, loosing 4 fish in a day, this happened on Tuesday this week. I did a big water change (50%) and cleaned both filters (in tank water). I did another water change and gravel clean with the siphon hose method plus cleaned the internal filter (in tank water) and had the water tested today (Sunday) and the nitrate level came back as extreme at around 80/100ppm. My question is this, how often can I safely do water changes to get the nitrate level down? Daily, every second day, every third day? Would raising the temp to 27deg c help? Any help to two very amateur fish keepers would be greatly appreciated. Thanks in advance.

 

Regards,

Paul & Maree 

Link to comment
Share on other sites

Hi Paul

I hope that you did not clean the filters too well as this will cause more issue. Only ever clean your filters in water from the tank and only lightly.

Nitrate Toxicity are affected by PH and temperature, increasing PH and temperature will protect your fish, a PH of 8.2 and a temperature of 28 or 29 is safe, as long as all your fish are African cichlids. I'm not sure how the cat fish will handle this.

I actually think you could do a 100% water change if you can keep the PH, KH and GH in the same range, but as you most likely do not have a large container to store water before using it you will need to do smaller water changes each day. Say 15%

 

Link to comment
Share on other sites

27 minutes ago, mjoconr said:

Nitrate Toxicity are affected by PH and temperature

Nitrate isn't toxic to fish unless we're talking phenomenally high levels.... and while 80-100ppm is high it's nowhere near toxic levels.

Nitrite on the other hand is!

OP: I wouldn't get "too" worried about nitrate levels but you should double check that you are measuring nitrate and not nitrite levels.

Even marginally high nitrite levels will kill fish and if they're going up or clearly measurable then

 1. you have too much food going into the system and hence too much ammonia being produced and hence too much nitrite for the bacteria to convert into nitrate

 2. or perhaps your nitrite->nitrate conversion process has broken down at least partially. A too-harsh filter-cleaning exercise perhaps or a dead fish causing a spike in material for the bacteria to consume or your water supplier found  a dead cat in the water supply tanks and gave it an extra high dose of chlorine or worse, chloramine that outlasted your water conditioner (or you forgot to use water conditioner?)

 

 

Things to do: 

 - reduce the food input; in fact probably don't feed at all for several days. The food gets converted to ammonia, ammonia to nitrite and nitrite to nitrate. In a freshwater aquarium and without lots and lots of plants or expensive stuff the the primary 

- reduce the temperature (no don't increase it to 27 degrees)

- water changes. The frequency and proportion of water changes depends mostly on the condition of the water going in. If it's aged, conditioned and the correct temperature you can safely perform a 100% water change. I keep a pair of 1000 litre water change tanks precisely for this reason, something similar (though obviously smaller) woudl be recommended for your purposes.

 - plants consume nitrates but from your description of tank size and occupants I doubt you'd be able to fit enough to have a significant impact

 

 

Link to comment
Share on other sites

1 minute ago, chorrylan said:

 

Things to do: 

 - reduce the food input; in fact probably don't feed at all for several days. The food gets converted to ammonia, ammonia to nitrite and nitrite to nitrate. In a freshwater aquarium and without lots and lots of plants or expensive stuff the the primary 

- reduce the temperature (no don't increase it to 27 degrees)

Toxic levels are both pH and temperature dependent. Toxicity increases as pH decreases and as temperature decreases. So increasing both these will help.

 

Link to comment
Share on other sites

Carbonate Hardness (KH) and General Hardness (GH) are the main factors which maintain the PH of your water.

Have read of this http://fins.actwin.com/mirror/begin-chem.html

African Fish come from water with high Carbonate Hardness (KH) and General Hardness (GH) so can handle it being high which will help reduce the effects of No3.

 

Link to comment
Share on other sites

I've quite often done successive 50 percent water changes with no ill effect though I do limit it to 2 days for a 100 percent change before I give it a few days to stabilize again.

For me I've found that if you constantly whammy your tank with new water that your tank can become unstable and you can introduce stress into your fish.

I always use a daily change that is capped at 50% and just reduce it from there to suit what your tank requires. Of course emergency situations can require larger changes but high nitrates (normally) I wouldn't consider requiring more than 50%

If you are getting really high nitrate readings over a 3 week period then chances are you are feeding your fish too much. Fish are opportunistic feeders meaning they will eat everything they can because in the wild it may be days before they get their next feed. Reducing excess feeding can allow your water changes to stretch a little longer if its becoming a chore.

Link to comment
Share on other sites

Hey, Thanks for the replies, I have read the information on the water conditioning and have a better understanding on how everything works. I will be changing the water a couple more times this week and get the water retested. Once again thanks for your help.

Cheers,

Paul

Link to comment
Share on other sites

On 1/17/2016 at 10:48 PM, mjoconr said:

Toxicity increases as ... temperature decreases. So increasing both these will help.

 

It's correct that for a given concentration of nitrite (or ammonia) the toxicity increases as temperature decreases *but* the input to this sequence is decomposition of nitrogen-containing substances and this *greatly* increases with increasing temperature thereby breaking the "for a given concentration" assumption.

To complicate things further, both ammonia and nitrate toxicity cause gill damage and reduction in oxygen absorption and the availability of oxygen goes down as the temperature increases. In  an african cichlid tank with poor/recovering/cycling filtration I'd be keeping temps around 22-23 deg.

Link to comment
Share on other sites

Sounds like to me, as you said, you dropped your game and let water changes and filter cleans get well past the maintenance deadlines.

 

Youve kept fish for 3 years, so you've likely had tap water close enough to being suitable as far as KH and GH goes.

But not water changing as often as you should and leaving excessive waiste inside your filters,,, basically is turning itself into a nitrate factory.

Simply cleaning your filter as you have will bring the nitrate production down dramatically, also cleaning out substrate helps if it's loaded with waiste.

I'd call daily water changes of 30% perfectly safe as I do this on my heavily stocked display daily and permanently, but be careful of dramatic temp fluctuations.

Wont take long at 30% daily to get nitrates back down.

 

If nitrate issues persist of climbing to fast, then feeding frequency or stocking levels may need reconsideration.

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

×
×
  • Create New...