Why fertilize?

[Alex Kadyshevich]

It's long been a question I've wanted to ask...why on earth do people buy and introduce fertilizers with nitrates and phosphates...when these are the very elements we do water changes to remove?

 

[Byron]

There is considerable misunderstanding when it comes to plant additives. The quality brands do not include nitrates or phosphates because as you correctly said, no one should be adding these to an aquarium. TNC Lite has all needed nutrients but no nitrates or phosphates; it is (so far as I know) only available in the UK. Seachem's Flourish Comprehensive Supplement has 0.07% nitrate and 0.01% phosphates. Brightwell Aquatics line is similar if memory serves me. These levels are so low they are not going to contribute to either problem.

High-tech planted tanks are different, nitrate is apparently necessary, but those with these tanks are more interested in plants than fish health. Nitrates do detrimentally affect fish, that is now known.

 

[Alex Kadyshevich]

Thanks so much for saying (pretty much) what I've been thinking. I bought a tropica package on amazon, with nutrient tablets (upset my establshed plants,) mostly because I bought a deep tank for aesthetical reasons, but as I'm a short man tricky to reach some parts.
A bottle of nitrate and phosphate did say for heavily planted tanks, so on reflection did a big water change to reverse. ( struggled with my usually reliable siphon..)
Planning to continue with the final bottle of trace elements and see how we go...
Bought Hygrophila and Hornwort to help, only hornwort growing, and vallis throughout tank having very different reactions.?

 

[Byron]

I have no idea of your level of experience or knowledge on this, so bear with me if this is old news. The first thing with aquarium plants is the light. The intensity must be sufficient to drive photosynthesis and this varied among plant species (high light, low light, and in between). High light plants just will not grow for long if the light is not bright enough. That is the first critical factor, and the second is nutrient availability. All 17 nutrients must be present and at sufficient levels in balance with the light (intensity and duration factor in here).

It is possible to have all nutrients available from feeding the fish and doing partial water changes. However, while this can work in one tank, it may not in another. The GH of the water is another factor. The more plants in the tank that are fast growing, the brighter the light and the more nutrient fertilizing will be required. And add to that the fact that not all plants will grow well in with certain other plants.

 

[TwoTankAmin]

The reason we add nitrate to a high tech planted tanks is pretty simple. Most plants want ammonium which is the normal form most ammonia takes in water. The bacteria prefer ammonia itself but can use ammonium less efficiently. In a high tech planted tank the plants will use up some nutrients and even CO2 faster. They can use some thing up entirely.

If one keep no fish etc., then one could feed their plants ammonia. But when that is not possible, we feed them nitrate. They can use this less efficiently because they have to convert it back to ammonia.

Bear in mind we are talking about well planted,m high light needing plants which also need added macro and trace ferts as well as CO2. And they will usually need lots of pruning. I kept one for almost 10 years and it was the most maint. intensive tank I had. I finally concluded what Byron noted. I keep fish not plants. I keep plants because they are good for the fish and the health of a tank.

I also keep a number of unplanted pleco tanks.

Whether one needs to add ferts of any kind depends on their water and then what and how many plants they keep.

 

[seangee]

The plants you mention need no more than the Seachem comprehensive or TNC lite that @Byron mentioned. Hygrophila can take some time to establish - but when it starts growing you just cut off the tops and plant them to get more the 2 pictures below were taken a month apart and I never added any new hygrophila in between - but did regularly snip and replant. Vals can take months to establish and won't grow in some tanks.

https://www.fishforums.net/data/attachments/96/96127-755a953e82a5744f330af9b39ebd039c.jpg
https://www.fishforums.net/attachments/20200721_164106-jpg.110373/

 

[10 Tanks]

It's long been a question I've wanted to ask...why on earth do people buy and introduce fertilizers with nitrates and phosphates...when these are the very elements we do water changes to remove?

Hello Alex. Your plants don't require more fertilizer than those produced by the fish. By feeding your fish a balanced diet, they'll provide all the nutrients the plants require when their waste dissolves in the tank water. Then, you change half the tank water weekly and that removes any forms of nitrogen the plants don't use and you maintain a clean environment for the fish and plants. Pretty easy.

10 Tanks (now 11)

 

[Alex Kadyshevich]

Well, many thanks gents. Between you you've given me much food for thought...and more than a few ideas. . I've had 2 tanks before, but this is my largest (75 gal) and the one I'm really trying to get right. My slow growing plants ( java fern, anubias, crypts) are doing well. Hope this thread is helpful to other confused folk

 

[TwoTankAmin]

One thing to consider. The nutriends plants need fall into two basic groups macro and trace. That is a bit of an over simplification but valid. The macros are the NPK - Nitrogen, Phosphorus and Potasium. Pretty much everything else falls into the other grouping. And this is why I like using the Tropica products. They now make two different ferts. The first Is a more comprehensive one which contains, it all. The second contains mostly the trace stuff.

A stocked tank can often provide all of the macros. For example, the nitrrogen comes from ammonia or nitrate. Most of the trace stuff tends to come in with our water. What ferts. one should use is a function of the plant load and the fish load. If you have a lightly stocked tank, you may need the comprehensive. But the same plant load with many more fish may mean that you only need the trace mix, if it needs anything.

On the other hand the type and number of plants one has also matters. The more of them one has, and the more demanding they are, then the more you may need the comprehensive no matter what your stocking level.

I keep both types of the Tropica fertilizers. It can take a little time to decide what and how much you need in any given tank. But once you get it basically dialed in, it is pretty easy. The only thing I rarely see mentioned in planted tank discusions is the need to modify the dosing of fertilizer as plants grow and then when you finally have a jungle and have to do a major prune. Then you may want to reduce you fertilizing.

I can also confess to the following. I have kept clown loaches for over 20 years. They started out in smaller tanks and then moved into a 75 planted. In that tank I had an outbreak of red algae that lasted for almost 18 years. It was that long because from that 75 they were moved to a 150 and the algae came along. Nothing I did knocked it back. That is until about a year ago. I stopped being as thick as a brick and finally realized those clowns were my macro ferts and I was dosing more on top of that. I stopped using the Macros and now only use the trace mix. I am now winning the algae war.

My biggest issue is that when anubias grow really tall, they get very close to the light and algae just loves that imbalance.

 

[StevenF]

Many people have issues with too much nitrate and phosphate. But not everyone does. When i set ups may small tank plants were slowly yiying and my my nitrogen was zero. Myphos-phosphate levels were offf the test kit color chart. frequent large water changes would not keep phosphate levels down. And the plants were still dying. I tried adding nitrogen, and that lowered my phosphate levels and my plants started to grow.

Doing water changes is not just about removing nitrogen and phosphate. It also replenishes nutrients such as Calcium and magnesium in the water. Calcium and magnesium if critical nutrients for plants. Without them plants will not grow. But most fertilizers don't have calcium and most don't have enough magnesium. Plants need 14 nutrients to grow. Ifjust one is missing your plants will not grow and will die. And in my experience if you have a one nutrient missing you likely will have algae issues.

Most fertilizers on the market don't have all 14 nutrients plant need to grow. Mainly because tap water typically supplies these nutrients. But if you have very soft water or ar using RO water many commercial aquarium fertilizers won't work.

ammonium which is the normal form most ammonia takes in water.

Plants can consume nitrogen from aammonia, urea, amino acids and nitrate. Plants don't prefer nitrate but if there are no other sources of nitrogen they will consume nitrate and grow well with just nitrate. I have gotten ver good plant growth with just nitrate in my tank. I use 100% RO water.