Help - tank levels not as expected in fishless tank

[CV26]

Hello. Newbie here - it is our first time with tropical fish.

We have a 100l tank and it's been running for a week. We used a dechlorinator and in the tank we have 5 live tropica easy plants, 2 large rocks, 1 small rock, 1 piece of bogwood, and small sized gravel. The rock looks like it is 2 different types (one cream/ light brown in tone and the other grey). We soaked the bog wood for a week and the water was clear before it went in the tank, the rock and gravel were rinsed well.

We visited several aquatic shops in preparation for getting the tank and nobody warned us that having unusual levels would be a risk with a new tank. They each said, set it up, wait a few days and add fish.

We went to buy our first fish today and were disappointed to fail our water test. Our Nitrites were too high for one thing. We bought a liquid test kit and have so far tested our tap water and the tank water again. We have since done a large (75% ish) water change and retested a few hours after that to get another baseline for moving forward.

The shop said it could be something in the gravel even though we thoroughly rinsed it. We're really confused and wanted to ask for any advice on what we do next. We are prepared to put the effort in to get this right but feel a bit lost as to our next steps...

Here are the results:

Home test before water change - PH 8.0, Ammonia 0.25, Nitrite 1.0, Nitrate 7.5

Tap water, nothing added - PH 7.0, Ammonia 0, Nitrite 0, Nitrate 7.5

Tank water 2 hours after large water change - PH 7.4, Ammonia 0, Nitrite 0, Nitrate 7.5

We have also noticed that the paler rock seems to have some black spots and we cant say whether they have always been there.

 

[CV26]

Having spoken to the shop where we got the tank, gravel, rocks and plants from, he is insisting it's more likely to be the one thing he didn't sell us - the bogwood.

Our options seem to be:
- Leave the tank as it is, keep testing and put in some bacteria balls if we start to see a rise in ammonia/nitrites. Do a normal water change in a few days, then continue testing in the hope that it becomes fish friendly.

- Remove everything into separate buckets and retest individually to try and see what is at fault. Wash out the filter to remove any lingering bacteria, scrub and rinse everything and redo the tank. Get back to 0 and then buy fish for them to start the cycle as we thought would happen.

- Something else?

Any help is much appreciated.

 

[Colin_T]

Hi and welcome to the forum

You could just leave the tank for 24 hours and see if any more ammonia or nitrite appear. If you do get an ammonia or nitrite reading in 24 hours then something is releasing ammonia. Then you take out the wood and big rocks and put them in clean bucket with clean tap water and leave them for 24 hours. If any of them have an ammonia reading that is what's causing the problem.

If you post a picture of the rocks we might be able to identify them.

 

[Byron]

My comment is just on the pH to explain the variances. When testing tap water, you need to ensure any CO2 dissolved in the water is out-gassed first. CO2 can dissolve in water as it runs through the pipes; CO2 produces carbonic acid, which means a lower pH. Out-gassing the CO2 removes this, and the pH test will be more accurate. It is often higher, depending upon how much (if any) CO2 was present, and the mineral content of the water.

So taking your numbers, where the tap water tested pH 7.0, and then was 7.4 and then 8 in the aquarium, this could be partly due to CO2 in the fresh tap water.

Another possible is dissolved mineral (primarily calcium) from one or more of the rocks, or the gravel. If any of these are calcareous, they will slowly dissolve, raising GH (general hardness) and pH.

To out-gas CO2, let a glass of tap water sit 24 hours, then test pH. Sometimes you can speed this up by very briskly agitating a small amount of tap water in a jar with a tight fitting lid. Really shake it for a few minutes, then test pH.

 

[CV26]

Thanks Colin_T

We are going to retest tonight to see if anything has shifted at all.

I'll come back later with the results.

Here are the rocks and a bit more of a close up of the black spots which may or may not have been there from the start.

 

[CV26]

Thanks Byron.

We did put a bit of spare gravel (so it hasn't been submerged for the week like the stuff in the tank) in some dechlorinated tap water last night and I've just retested that.

Ammonia and Nitrites at 0, Nitrate at 7.5 again and PH at 7.4.

Would PH climb higher over a few more days through this CO2 loss process or does it stabilise pretty quickly once its been out of the tap for a day?

Im conscious our reading after a week was 8.0 so I was wondering if that was more likely to be a rock issue perhaps or could just be the natural tap water PH after the CO2 has left 100l.

 

[Byron]

Thanks Byron.

We did put a bit of spare gravel (so it hasn't been submerged for the week like the stuff in the tank) in some dechlorinated tap water last night and I've just retested that.

Ammonia and Nitrites at 0, Nitrate at 7.5 again and PH at 7.4.

Would PH climb higher over a few more days through this CO2 loss process or does it stabilise pretty quickly once its been out of the tap for a day?

Im conscious our reading after a week was 8.0 so I was wondering if that was more likely to be a rock issue perhaps or could just be the natural tap water PH after the CO2 has left 100l.

Either or both reasons might apply here. The tap water out-gas test is easy and will confirm or refute that as a source, so then it would be the rock/substrate if the pH does rise.

CO2 out-gasses from water in 24 hours, provided it is left open to the air.

 

[CV26]

The gravel test was standing water in an open jug for 24 hours and it read 7.4 today.

That sounds like something could have contributed the other 0.6 that gave us a final read of 8.0 after a week in the tank then. I've read vinegar can be used to fizz test for calcium rocks...will brown vinegar do for a really basic test?

 

[Colin_T]

The rocks look a bit like limestone. To test this pour any sort of vinegar on the dry rock and see what happens. If the rock is calcium based, the vinegar will react with the calcium/ lime and foam and bubble away. Limestone and sandstone will cause the pH to go up.

 

[CV26]

Thanks both for your advice. Will report back soon with some further results.

If the rock is a problem what's the etiquette for returning it to the shop? Odd question I know but as it's a natural product would a fish shop be up for swapping it if it's leaching calcium? I only ask because they are weighty pieces and we were charged by the kilo they cost a bit.

 

[Byron]

As Colin said, vinegar is one test for calcareous rock. It is a fairly weak acid though, and may not always be sufficient, but try it first and if there is fizzing, calcium is present. Should another acid test be necessary, the Regent #2 in the API nitrate test is a stronger acid that is often suggested for this. But do the vinegar first.

There is nothing wrong with calcareous rock, provided you have harder water requiring fish (livebearers, rift lake cichlids, some rainbowfish, a few others). The rock will very slowly dissolve, raising GH and KH and pH. But if you intend soft water species, this is not advisable. The initial source water pH of 7.4 is fairly adaptable for many species, but if it climbs to 8 this is not as good.

You should also confirm the substrate gravel...the white in that coould be calcareous. Did it come in a bag, with data on the material? Or is it online somewhere?

Edit. BTW, it would be advisable to ascertain the GH and KH of your source water, as these are connected to pH. Fish are more directly impacted by GH (whether soft or hard, depending upon species). Might be data posted on the website of your municipal water authority. GH is general or total hardness, KH is carbonate hardness also called Alkalinity.

 

[CV26]

We have shortlisted platies, guppies, neon tetra and cories.

I dont have the original gravel bag but I think it was this one...http://www.aquaone.com.au/2018-02-20-00-40-42/decoration-3/gravel/item/2623-12221

 

[Colin_T]

with a pH of 8 you should drop the neons and stay with the livebearers.

 

[Byron]

Agree. Not much info on that site; "safe" means nothing, as calcareous gravel would be safe but not good for soft water fish.

Cories could have a problem though, they should be over sand.

If you stay with livebearers only, the rock and gravel are not a problem at all. Tank was given as 100 liters (26 gallons), so among livebearers the guppies and platies are OK. [Swordtails and mollies get too large for this tank.] There are also Endler Livebearers, related to guppies but smaller.

Avoid females or you will have more fry than you can manage every month. All males will be best, whatever livebearer species.

 

[CV26]

Really appreciate everyone's time. Thank you.

We are really keen to find out what's causing the changes and as we dont have any fish yet we have the luxury of messing around with the tank to find out.

A fresh test of the tank gave use the 7.5 Nitrates, and the PH had shot up to 7.9/8.0. There may have been trace amounts of Ammonia and Nitrites but not a full mark up the API test for either. It was hard to tell.

We've decided therefore to run separate tests to see what's causing the PH issue. We'll keep it going for a few days to see what the Ammonia levels do too.

Bog wood and rocks have been separated out. None of the rocks fizzed using distilled white vinegar and neither did the gravel. We've also taken out most of the water in the tank and replaced it with fresh stuff to see if it's the gravel.

Whatever is doing the PH could stay and we stick with livebearers, but we'd like to know the cause so we can make as best of an informed decision as possible.

Maybe an extreme step but we'll see what happens over the next few days and what is most likely to blame for what activity.

Thanks again and I'll come back with more results soon.