Multiple Filters/Excessive Filtration Increases Stocking Density?

Hey guys, completely new here but not entirely new to fishkeeping.
I've recently bought a 64ltr tank complete with everything I need. The filter that came with it I really don't like and am probably going to replace/add a Fluval U2 or a Fluval 106. I was just wondering if this would increase my stocking density. The article on this site on stocking density says it would indeed allow me to add almost twice as many fish. Has anyone here had experience in this though?

Thanks in advance

Awesome! Thanks for your help, I reckon I'll just grab the U2 and leave it at that.


Thanks again :-)

Yeah I will do, haven't even started cycling it yet. Another question if thats ok, completely unrelated. I want a paradise fish in there eventually as well as either bleeding heart tetras or celestial pearl danios. The more I read around Paradise fish the more conflicting opinions I get. Would they be super aggressive towards the smaller shoaers? Or will the shoalers be fine as long as the tank is well planted?

Thanks again.

Who on earth came up with the idea that a heavily planted tank requires a filter that changes the water at least 10 times an hour? It seems totally absurd. First of all, I very much doubt if most plants would thrive, or even survive, in the speed of flow that would cause. Virtually all aquarium plants come from still or very slow waters, indeed most of the commoner ones are actually marsh plants rather than true aquatics. Second, it is clearly assuming that the filter bacteria are entirely responsible for dealing with fish ammonia, whereas one of the major reasons for having a densely planted tank is that the plants will do a large part of that work. On this basis, filtration can be reduced in a well-planted tank rather than increased. I suspect that this idea arise from some concept of "dead spots" where the water doesn't circulate because of the dense planting. While this might possibly occur in a very large tank, I don't think it at all likely in any domestic size aquarium. I've had a good look in all the corners of my tanks, which have "normal" levels of filtration, and I can see water movement everywhere. In any case, as noted above, the plants will deal with any ammonia or whatever. Even with no water movement at all, anything in the water will spread surprisingly quickly by diffusion alone. I think the idea of dead spots is one of those greatly exaggerated remote possibilities. If you are still worried, two smaller filters, one at each end of the tank, would probably be a better bet than one big one.

I also think that too much filtration can be a bad thing in that it is generally results in increased flow rates through the tank. Three of the used tanks I bought came with oversized filters. In each case, when I tried running these in those tanks the amount of water movement was ridiculous, far more than most fish would find comfortable, while the plants were flapping around like palm trees in a hurricane. There are many videos of people's tanks on YouTube etc., where one can see small fish (usually tetras) being subject to constant buffeting by a current which is far stronger than they like, subjecting them to continuous stress. I don't think many fish would be happy with a filter rate of 10 times per hour. More is not always better.

As far as stocking levels are concerned, if your tank is working OK then it is not overstocked, whatever any guide might say. This means regular water testing, but also observing your fish to make sure they are getting on. There's more to stocking than ammonia and filters. You could have two small fish in a big tank, but if one is making the other's life a misery by constantly chasing it, it could be argued that the tank is overstocked by one fish. Conversely, if you have only one or two of a type of fish which should really be in a shoal of six or more, then it might be said that you are understocked.

Awesome guys, thanks very much. I've kept dwarf gouramis before and just wanted a bit of a change. It looks like I'll end up getting one though as a feature fish. Unless there are any other suggestions? I hope to include some form of dwarf corys aswell.

Yeah I've made that mistake before with corys and the substrate. At the moment I have a about a 70/30 mix of sand and small aquarium gravel so they should be fine. As for your suggestions thats exactly what I intend on! A nice shoal of dwarf corys, a group of Bleeding hearts OR Celestial pearl danios (If I can get hold of some) and some form of slightly larger fish. Like you've said a Honey or Dwarf gourami would be ok but I've kept them before and just fancy something different... Although there isn't much choice for 64ltr

I love the look of chocolate gouramis as well but I decided against them for some reason... I think it was because of the water quality.

Awesome! Thank you so much for your help!

You like heavily planted tanks and as such will see different behaviour from lighly planted tanks (and I include tanks with a few synthetic plants). You are unusual in having planted tanks. The majority of newcomers to fish keeping seem to go for the synthetic only/very few live plants option. I know about these latter tanks - they are the kind I have. You have the experience to advise people with heavily planted tanks, I don't.
In my type of tank, zebra danios will be very active and need plenty swimming room. There aren't enough plants to keep them occupied. Putting a shoal of danios in a 40 litre tank with one plastic plant is not a good idea, though from the size of the fish they look as though that sized tank is perfect. But put them in a very heavily planted tank and they'd probably do well. I should get into the habit of asking newcomers about what is in the tank in terms of plants and decor.

I do 25 to 30% water changes a week on all my tanks as I have KH of 3 german degrees/54ppm. I have suffered pH crashes in the past when I got lazy about water changes and didn't know any better  Rather than add remineralisation salts to the tanks, I decided to cope with this low buffering with water changes, which has worked well so far. My KH is so low that even with water changes during a fishless cycle, the pH dropped overnight from 7.4 to off the bottom of the scale.
Would I have the same problem with a heavily planted tank?




I have ember tetras in my 125 litre tank. They are so much nicer than the photos on-line; a much deeper, glowing orange compared the the washed out pale orange in the photos.

My water doesn't fit into nice pigeon holes, unfortunately. After standing 24 hours, my pH is 7.4/7.5, so alkaline. My GH is 6 to 7 German deg/108 to 125ppm, so that's classed as slightly hard. It's just the KH that's very low. The API GH and KH testers correspond with what my water company gives for hardness and alkalinity, so I know my testers are pretty accurate. I have no problems with snail shells eroding so there is enough calcium in my water supply and the pH is high enough for them.
Would the pH and GH affect my plants differently, despite the low KH?

My son used to work for a water testing company and he tells me that when water companies talk about hardness, they mean divalent metal ions and in the water supply that's calcium and magnesium ions. When they test alkalinity they measure of the amount of a particular acid at known concentration that is needed to drop the pH of a water sample to 4.5 (I think that was the value he said) so it is a measure of buffering capacity. Since the alkalinity measurement on my water company's site is almost identical to the KH I measured, it would seem that the KH tester is doing the same as the water testing lab's method for alkalinity.

I have no idea what the anions are! Our water is supplied by Northumbrian water, from their Kielder reservoir. If you have any idea what the rock around there is like, please let me know 
Edit: Just found a reference saying the base rock is the whin sill, ie dolerite composed mainly of pyroxene and feldspar


I have no problem at all growing java fern. It started as one clump bought from a shop, now it is growing well in all my tanks. I finally have some java moss growing and also something called spikey moss which was given to me. There is a small clump of anubias, a dwarf variety, which is holding its own - it doesn't grow any bigger but it doesn't disappear either. You will, of course, have noticed that none of these plants are planted in the substrate.

I would like to try growing some floating plants again. Do you have any suggestions for what would do well in my water?