Filter Advice Please

A pH crash isn't caused by a too small filter, it's caused by a low KH and not enough water changes to replenish the lost buffering capacity.

Do you know the General Hardness and Carbonate Hardness of your water? This is the starting point to sorting this problem out.

Hello

Okay so I contacted the water department and they said my General Hardness was described 2 ways. the GPG 5-7 and the PPM of 83-12-.

The Carbonate Hardness was given as 3.

Does that help?

Your main problem is your KH. 3 is very low; it's the same as mine and I know that I'm in danger of a pH crash - I had one about 8 years ago.

Nitrate, the end point of the nitrogen cycle, is acidic. Other things excreted by the fish are acidic. If you have wood in the tank, tannins released by that are acidic. The natural tendency of a fish tank is to become acidic over time, as shown by a falling pH. Carbonate reacts with acid. If there is a lot of carbonate it takes a long time to be used up but with low carbonate hardness it gets used up quickly; there is nothing left to react with the acids (ie nothing left to buffer the water against pH changes) so the acid level builds up, shown by a fall in pH.

The way to stop pH crashes is by adding carbonate. The simplest way is by regular water changes. When my pH crashed I was very lazy about doing water changes. I would go three or even four weeks without a water change. Since then I have done weekly water changes of at least 25% without fail. 9 days is the longest I will allow. I haven't had a pH crash since then.
Other methods are to add something made from calcium carbonate to your tank - this could be crushed coral (in your new filter when you find one), limestone rock, shells etc. Or you could add remineralisation salts of the kind added to reverse osmosis (RO) water - though you have to be careful to build up slowly and add exactly the same amount per litre at every water change.


Can I go back to the start please.
How long have you had the tank?
Did you cycle the tank with ammonia before getting fish?
Do you have any fish in the tank now?
What size is the tank (volume) to see what filter would be suitable?
And before the pH dropped, how often and how big were your water changes - size in terms of % of the tank volume.

Your concerns over your filter could be justified - I hate those filters that just have cartridges made of a fabric of some sort with carbon inside. Once we know the size of your tank, we can see if we can suggest a new filter.
Carbon does not really remove plant nutrients as they tend to be ions which don't bond to carbon. Carbon removes things that bond covalently, so if there is something organic in your plant additive, it would remove that but not trace minerals.

Is the cloudiness white or green? White is bacterial bloom, green is algal bloom, microscopic algae floating in the water.

I asked about timescale, cycling etc as white cloudiness is usually a bacterial bloom which is common in new tanks, but these are not the same bacteria we need to grow in the filter. They are harmless to fish, but can cause problems as they use a lot of the oxygen in the water. Doing lots of water changes will help to oxygenate the water temporarily as adding water churns up what's already in the tank, but doesn't do much for the cloudiness as these bacteria multiply faster than anything we can do to remove them. But as long as your filter outflow ripples the water surface there should be enough gas exchange going on for both fish and bloom bacteria. And going cloudy after 7 weeks is a bit unusual unless you had plant problems just before then as dead or dying plants matter is organic and will feed the bloom bacteria.

Algal blooms are caused by ammonia and other plant nutrients in the water. The usual remedy is to completely wrap the tank with something that blocks out all the light and to leave it there for 3 days. This deprives the algae of light which kills them.

Can I ask what type of testers you are using, strips or liquids? It is strange that you have a nitrate of zero, though not shaking one of the bottles in a liquid tester does give false results. There is usually nitrate in our tapwater, varying from very low up to as much as 40ppm, and the filter bacteria also make it from the ammonia excreted by the fish. Strip testers that you dip in the water are known to be inaccurate.
Gasping at the top of the tank is lack of oxygen - but it is not necessarily due to not enough oxygen in the water. Ammonia burns the fish's gills making it hard for them to absorb oxygen, and nitrite binds to their red blood cells stopping them carrying oxygen. To the fish both feel like they can't get enough oxygen so they gasp at the surface.
Despite your test results, I do wonder if you had some nitrite and/or nitrate as both of these are acidic and coupled with your low KH could explain your drop in pH and the fish deaths. The Equilibrium you have been using sounds like it is the kind of remineralisation salts that you use with RO water (I just looked at Seachem's website). It should be OK. I think.


I do need to make a comment on your fish. 25 litres is a small tank - I have a 26 litre tank for my betta. Small tanks are hard to keep the water stable. If something goes wrong, it goes wrong fast. You had a lot of fish for the size of tank. It doesn't matter what the size is when you buy the fish, it's the adult size you need to take into account.
Otocinclus are shoaling fish, you need at least 6 of them but a 25 litre tank won't be able to produce enough algae for 6 otos. They should really be added to a mature tank that has had time to grow algae for them to eat.
Guppies are OK provided they are all males. If you have any females you will soon be overpopulated with fry.
What were the red tetras? If they were ember tetras, fine, though you need at least 6 of them. Any other red tetra will grow too big for 25 litres.
Julii cory. All cories should be in a shoal of at least 6 of the same species. There are only three, maybe four species suitable for a tank your size and I'm afraid juliis aren't one of them. Yours would also have probably been trilineatus as that's what nearly all the cories labelled as julii actually are.
A snail is fine.

Do you have any fish at the moment? Are the fish you listed what you have, or what you had? If it's what you have, could I suggest you rehome the cory and find out what the red tetras are.

I'm not very good with plants but I think that you don't need the Flourish Excel unless you have high lighting levels, something that small tanks don't usually have. Hopefully one of the plant experts can help you with them.

The simplest thing you could do to stop another pH crash is a combination of more water changes - twice a week, which shouldn't be too difficult with 25 litres  - and add a source of calcium carbonate to slowly dissolve and boost your KH. Something like a limestone rock, or shells, or even crushed coral, though a small tank will have a small filter and there won't be room inside for any coral.

I would also see if you can trade your cories, which grow too big for your tank and need to be in a group of at least 6, for some more of the same species of tetra as they also need to be in a group of 6+.


You asked about filters in your first post. But you mention the price of tests in $ so I presume you do not live in the UK. This makes it tricky to know what to advise as I only know filters available in the UK. I am aware that there are a lot more HOB filters available in the USA than here, and that most of them have just those carbon filled cartridges. There is one make that is usually recommended as the media can be customised easily in that brand. I'll see if I can find which one it is.


Edit - Aquaclear HOB filters. They have foam, carbon and biomax media according to the manual. You could either use the carbon or swap it for a sponge of any make cut to fit. If you decided to go for something like this, put your existing cartridges in place of the carbon that comes with the new filter.

From what Seachem's website says, Equilibrium looks OK, they do list it in the 'RO Mineral replacement' section. Though it does say Equilibrium is for planted tanks, Replenish seems to be the main RO remin product.

You should be able to get coral and shells from shops that do marine fish. Those sold as ornaments could be treated with some sort of resin, and those from a beach could be contaminated with pollution - and there could be local laws prohibiting collection.

If the old filter media is first in the water flow that will help transfer any loose bits of bacteria-rich biofilm into the new media. Leave it 6 weeks, and keep an eye on your ammonia and nitrite for a few days after you remove the old media, just in case. If there's more than one bit of old media, remove one bit at a time with a couple of weeks between.

It is better to leave the pH well alone. Doing things to alter it, before or after it's in the tank, can cause more problems than it solves.

What is the pH of a sample of tapwater that you've left standing overnight? If that is a lot lower than freshly run water, it might be an idea to let your water stand overnight before adding it to the tank. If ther's not much difference, the way round it is to do a few small water changes a week instead of one larger one. That way you don't add very much higher pH water at any one time.