Basic guide on the interaction between Nitrates, PH, and alkalinity

This is an article I wrote for Conway Tropical Fish's newsletter.

Did you know?
That when ammonia is digested by your aquarium, and turned into nitrite, then nitrates, it produces acids? It produces hydrogen ions, which without something to combine with, will acidify your water. Which means it'll make the ph in your aquarium will become softer, or lower, or more acidic. However you prefer to look at it, this is hard on all fish. Luckily most water comes out of the tap with something to help with this. This is the measurement of alkalinity, or buffer. This number on your test kit, shows you how much buffer is currently in your water. The buffer is the other part of the equation, mix your acids, with the buffer, and they cancel each other out.

So let's recap, our fish goes to the bathroom, and it turns into nitrates, which during that process made some acids. Our water neutralizes that hopefully. What happens when you produce more acids than your water can neutralize? Our PH will start to drop. Which we've established is very hard on our fish. There is no bottom to how acidic the water will get. Once you're out of buffer, every time you feed, you'll be lowering the PH slightly.

A great way to think about this process, is to use a bank account as an example. You have $100 in the bank, this is your buffer(alkalinity). Every time you eat lunch(nitrates) it'll cost you $5 dollars. With this example, we can see that we can have lunch 20 times, then we'll be out of buffer, and then every day after that, we'll be going into negative numbers.(lowering PH) We need to get more money(buffer) so we can keep eating!

To regain buffer in an aquarium it's easy. All we have to do is do a water change. We'll continue to use our 100 buffer example. If we have 0 buffer left, and change 30% of the water. We'll then have $30 to spend on lunches. 6 more days of eating. As you can see with this example, we'll be changing water roughly once a week to keep up. This is would be a fairly heavy stocked aquarium.

Tips to maintain the balance:
1. Control the food, big fish, or many fish, will result in more waste. If you can eat for $1 every day, You'd only have to do a water change once a month to maintain a nice balance.
2. Quality of food, $3 in potato chips, will not last nearly as long as a $3 sandwich. A high quality food, will take less food, to give the fish the same amount of nutrients. Higher quality foods, have less fillers. Fillers tend go through a fish with no benefit.
3. Maintain a water change schedule. Don't go into the negative. If you make $30 from a water change, and your account is overdrawn by $60 dollars, it'll take you 3 water changes just to catch back up. All the while, your fish will be under very heavy stress, it may result in some losses.
4. Ph buffer, when used correctly can help. This will temporarily alter your buffer. Think of it like a loan. Many buffers only last for a few days to a week. In most cases, if you need a PH buffer product in the aquarium, it is a lack of maintenance. We can keep taking loans, to eat every day. However, nitrates in the aquarium will build up, until they overwhelm us.
5. If your tap water has very little buffer to start out with, crushed coral can be used effectively to add some buffer to the water. It will dissolve slowly, with each water change.

Water changes are a good thing, however there is too much of a good thing. If your fish are not used to it, gradually increase the frequency of water changes. 30% is always safest. Some people will change more water each time, it can cause stress, we find that 30% works well for us. Don't rush out and change 80% of your aquarium water today. Instead do 30%, each week for a month. Then observe your fish next month and see that they're more lively, have better colors, and may even be breeding now!

***This is a basic guide, there are other things that come into play, however once someone has mastered this maintenance routine, they will be able to keep healthy fish for a long time. I know that eventually, even with this routine you'll fall behind, because you're changing percentages of water. You only regain 30% of the buffer. if it's 30% of 30 dollars. Then you'd go from 70 buffer left in the aquarium to 80 buffer, from a 30% water change. Likewise, if you're in the negative. This basic guide is to help people realize it's a give and take system. In the aquarium it would always be better, to give more water changes, than needed.

This is a great guide, thanks for posting it up Cory!

good read. Thanks!

I had a problem with the pH dropping rapidly recently in two tanks. I lost 5 Bolivian Ram babies and had a second tank with a very low pH but didn't lose anything from that one. The odd thing here is that I have been doing weekly water changes. The ram babies were in a 5 gallon tank and about 50% weekly. They had been in the tank for about three months, grown to about 1" and there were no other fish in that tank. The other tank is a 55 gallon with a pair of Bolivian Rams ten juvenile apisto's and a dozen Rummy nose. I do weekly water changes of about seventeen gallons. Within one week my pH dropped in both tanks from about 7.4 to 6.0 or lower (my test kit only reads to 6.0). None of the feeding conditions changed, no increase in amount or change in type of food. I did a 50%change in the 55 and got it back to 6.4, added buffer over a week to get the pH to 6.8. With the buffer pH is holding steady but now I add buffer with each water change.

Do the utilities change water sources from well water to snow melt in late spring? I've only been back into the hobby for 8 months and this is the first time I have seen this type of problem.

Guest wrote:good read. Thanks!

Danrobnett wrote:I had a problem with the pH dropping rapidly recently in two tanks. I lost 5 Bolivian Ram babies and had a second tank with a very low pH but didn't lose anything from that one. The odd thing here is that I have been doing weekly water changes. The ram babies were in a 5 gallon tank and about 50% weekly. They had been in the tank for about three months, grown to about 1" and there were no other fish in that tank. The other tank is a 55 gallon with a pair of Bolivian Rams ten juvenile apisto's and a dozen Rummy nose. I do weekly water changes of about seventeen gallons. Within one week my pH dropped in both tanks from about 7.4 to 6.0 or lower (my test kit only reads to 6.0). None of the feeding conditions changed, no increase in amount or change in type of food. I did a 50%change in the 55 and got it back to 6.4, added buffer over a week to get the pH to 6.8. With the buffer pH is holding steady but now I add buffer with each water change.

Do the utilities change water sources from well water to snow melt in late spring? I've only been back into the hobby for 8 months and this is the first time I have seen this type of problem.

Hi Danrobnett,

Depending upon where your are it it likely that your water source changed; possibly the physical location of the source or possibly the chemistry.

A second way to use up the ammonia, nitrites, and nitrates and decreasing the effects of feeding is by adding live plants to your aquariums. Live healthy plants gobble up all three of the chemicals listed. Typically plants prefer ammonia but if ammonia isn't available they will eat up nitrites and if nitrites aren't available they will utilize nitrates. Plants don't only look good in an aquarium, they help improve the environment by absorbing the waste by-products the fish produce.

I am not saying that planted aquariums don't require water changes because they do; but a well planted aquarium can help minimize the effects that Cory was describing. Best of all, plants will grow faster if there are excessive nutrients and slower if there are less so they can 'adjust' to the conditions.

[You must be registered and logged in to see this image.]