advice about a rather small tank? 6 g

dorabaker

I have a 6 gallon tank which I've been using as a betta tank for some time, with only plants (Elodea) as filtration, and no substrate. I've been regularly changing around 50% of the water a week and generally trying to take as much care of it as possible. I've asked about whether it's ok to use plants instead of filtration for a 6 gallon betta tank on here before, and have been told 'yes' by some very experienced fishkeepers.

But unfortunately, the same thing has happened to all the bettas I've kept in there - they've started off incredibly happy and healthy and their colors have improved massively from how they were in the pet shop, but after a few months they mysteriously begin to get lethargic and stressed-looking, and eventually die.

I can't figure out why this is happening!

Certainly everything goes very well for a few months. I can't understand the eventual decline. Unfortunately I can't afford a nitrate/nitrite test kit - they are INCREDIBLY expensive and I am broke - so I can't tell you what the levels of these toxins are in the water. However, I have noticed that the pH gradually gets more and more acid in the tank, despite my substantial weekly water changes.

I am thinking of getting some gravel and more plants for the tank (namely Java Moss and cryptocorynes, and some floating Java Fern to replace the elodea) to provide a subtrate for beneficial bacteria, but I don't know if that would solve the problem.
While I'm at it, any ideas about suitable fish (apart from bettas) for a tank this small (assuming I ever work out how to stop them dying)? I love small shoaling fish but please don't suggest corys as I've had a lot of bad luck with them

P.S Since this post is full of a lot of bad news, I thought I should add something positive as well..my main tank is absolutely flourishing at the moment, despite greatly reduced numbers of fish (or perhaps because of that!) and I'm looking forward to replenishing my supply of Cherry Barbs eventually. For those who don't know, the main tank fell into decline and a few fish died after I had a lapse with my water changes. Lesson learnt and water changes regularly every Wedensday now :)

Kim

Your 6 gallon tank is probably suffering from a buildup of ammonia. Although the plants will use some of this toxin, I'm going to guess that they are not growing fast enough to absorb it all. When this happens, ammonia will build up over time unless 100% water changes are performed.

To use simple numbers, let's say your fish produces 1 ppm of ammonia each week, so by the end of the first week you have 1 ppm of ammonia in the water. You do a 50% water change, cutting this number down to .5 ppm. By the end of the second week you have 1.5 ppm ammonia in the tank (.5 ppm that you started with and 1 ppm from fish waste during the week). You then do another 50% water change, but this time the number only drops to .75 ppm. One week later and you have 1.75 ppm, which is reduced to .875 with a 50% water change. Subsequently, the ammonia in your tank is rising despite the continued 50% weekly water changes.

Since your tank has plants (which use some ammonia) and only a single betta (low bioload), this process will take longer, which is likely why you are getting fish deaths several months after their purchase. I would highly recommend you get a small filter (sponge filter or something like an azoo palm filter which only costs around $8-9) and cycle the tank with pure ammonia before bringing home another fish. Of course, this requires a test kit for ammonia, nitrite, and nitrate, but you could probably get a better price online if cost is the issue. Also, these products will help you with your other tanks, so I would try to purchase them before adding any new fish anyway.

Hope this helps!

DragonFyre14

It does sound as if the ammonia is building up. So I'd suggest either getting a small filter, or you could just add some gravel and another plant. The gravel (and the filter if you go that route) give the beneficial bacteria a place to grow. with a bare bottom tank and just a plant, there isn't much space for it to accumulate.

Jakiebabie

Totally agree. Consider the surface area of the bare bottom compared to all the round surfaces of an inch of gravel. Gunk can still build up in that gravel so you do have to be careful of that too but there is a huge area for beneficial bacteria to cover. Yes a couple more plants would help! Also you could do 2 water changes a week for the Betta rather than 1 per week. Again small moves step up the quality of the water.
Don't over feed too. Depending on his size, 2-3 pellets once a day. How often do you feed them normally?

Byron

Most fish tanks need a substrate. The bacterial activity that occurs down there is very important, and I'm thinking of more than just the nitrifying bacteria. In this case, sand would be fine, or a fine gravel. And then some substrate-rooted plants. Together this should solve the problem.

I am not certain this is only ammonia; nitrite is also a possibility, and nitrate. All of these would benefit from the above.

Byron.

dorabaker

Thankyou so much everyone, I had a feeling it was an ammonia/nitrite buildup but wasn't sure why. I'll get some subtrate and plants and see how that goes!

dorabaker

my bettas (all have been females) are always tiny so I only feed them a tiny sprinkle of crushed up flakes each day, their stomachs aren't big enough for any more than that...