Hey there!

Wondering if anyone has any advice for me please. I have a 220L 6footer 'column' tank and Im new to fishkeeping :D

Over the past 3 months I have been maintaining my water parameters using a complete kit and after a month got 6 neon tetras and had no problems. They were so tiny in my big tank I had to get some more haha! Spaced over 2/3 months I got another 6 neon tetras, 7 male guppys then 6 mixed platys.

My problem is this - over the past few weeks (3 months into aquarium life) I have noticed a major decrease in the number of my Neon Tetra, some of the smaller ones didnt grow to full size like the others so maybe they didnt eat enough? They like being at the bottom on the tank. Anyhow Im pretty sure there is only 7 now and only 1 neon floated to the top the rest have 'disappeared'.

I did notice when they were resting there was a small neon with his tail missing - he seems to have disappeared now like the others.

Is there any chance the other fish could have eaten/bullied them? Now ive only got around 7 Neons Im afraid to add any new ones to add to the shoal in case they are picked off.

Any thoughts would be much appreciated! :)

Hi Loubie and welcome to FK

Could we ask for a little more info please before we start advising? Best to rule the main contenders out first.

Can you post tank readings for pH, GH, ammonia, nitrite and nitrate?

You have a bit of a mix there of soft, acidic water fish and hard more alkaline loving species. It's likely one of the groups won't be too happy.

Although those tanks do look big, given the limited surface area for gaseous exchange stocking will be rather limited.

Does it look a bit like this one (scroll down):
http://www.aqualease.co.uk/page/62/column_aquariums.htm

How do you ensure all of the fish are feeding?

Thanks Violet

I have been taking readings of the tank at least every week since I started. PH has always been 7. Ammonia has always been the lowest possible reading (0.1?). My Nitrite levels were a little high in the first month but I have combatted that and they are now the lowest reading possible. My Nitrate is now the one I keep an eye on the most but it is still within reasonable levels and I do frequent 20% water changes every 1/2 weeks (obv adding in 'Safe Water' so no metals/toxins etc). I trust the above is enough information? Sorry I cant give you the figures exactly right now.Plus could you enlighten me to what GH is?

Yes I read about the hard/soft/acidic/alkaline water in another thread and did not realise it could vary so much from each species! Probably because if the aquarist sells it in your area you presume it will be fine for you to do the same. I know we have hard water in the Midlands so its not best for the Neon Tetras.

Regarding the tank - it is similar to the last one '6foot column' I have been feeding them flakes from the start but I recently queried this with a local store because some of the fish's poo was rather long and white - he didnt think it was an internal parasite rather their diet. I also have a holiday block (gel) in the bottom that didnt dissolve while I was away so Im feeding them microwafers for a bit (sink faster) 3/4 times a week in the hope that they will discover the holiday block too! Other than that I just tap on the lid and most of them usually come to the top (Neons seemed to stop doing that after other fish were introduced, so they tend to go after it in the bottom half of the tank)

Neons don't fair well in hard water IMHO (GH = general hardness) and it's likely the elevated nitrite you were experiencing caused some health issues also.

Ammonia and nitrite should always read zero. I assume you did a fish in-cycle (as opposed to dosing liquid ammonia, the pretend fish, for a month or so)? Many fish don't make it through this process and small little bodies will be eaten quite quickly by tank mates (awful I know!)

Water changes ideally should be weekly, don't be tempted to skip, as they do more than just reduce nitrate.

I'd remove the holiday block if you can (do you need scuba gear in that tank?) as it will only be adding to potential water quality issues. Automatic timers are far better and safer if you are away