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Long post regarding my tank


16 Jan 2023
Some advice appreciated.

As some of you know, I started my aquarium in late Jan of this year.

Throughout the last 6 months I have found it pretty hard. I have lost lots of fish, and I take responsibility for this as I have escaped and upgraded my aquarium during this time.

At the moment I have a 160L aquarium and the stock is as follows:

  • one male molly
  • one female molly
  • 1 Molly fry
  • 3 corydora
  • snails - so many of them!

Within the last month I have lost two Molly and a Cory. One Molly developed a weird sore on her head and died within 2 days - I then treated the tank with Esher 2000 encase of any infection.

Then about 2 weeks later, I found one Molly had jumped out of the tank (I have ordered a net to cover the tank) and one Cory (this was one of my younger Cory, they did have just one eye when I got them) dead on the bottom of the tank,

Then another 2 weeks, and in the past two days two of my three Molly fry died. (The fry are kept within the tank but in a breeding box for protection and to ensure they can get enough food).

I am very disheartened by this but will keep going.

My male Molly is pretty rowdy, often chasing the female and also always goes after the Cory's food.

So questions:

Obviously I know I need a few more Cory and female Molly to keep them happy, should I wait a while longer until things settle in the tank? Or would it be better to even out the group sooner?

My remaining Molly fry is about 6 weeks old, still very small but I don't think could fit into the other fish mouth. Just worried they may get bullied or miss out on food if I can't find them hiding.

At some point soon I am going to be changing the sideboard they are on, as the one they are on is proving unstable. To move the tank I will obviously have to drain the majority of the fish tank, pop the fish in a bucket and do a BIG water change. How can I make this as LEAST stressful for the fish?

I am getting a fair amount of algae (there is a blue/ green tinged algae that sits just under the sand and I can see it through the glass, I try and move the sand regularly to keep the algae from getting oxygen). And lots of hair like thin algae that I am constantly fishing out of the tank. Due to my plants it tends to grow in and around them so removing it is hard.

At some point I want to move to more carpeting plants and smaller, lusher plants - I will consider adding co2 but to do this will essentially be another escape so I am trying to hold out as long as I can because of all the issues I have had.

I love my tank and my fish but just finding it very stressful and don't feel I have really got a stable tank yet :(

Some photos of the algae for reference.



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Choose one incredibly simple plant: my suggestion would be bacopa / pennywort, and put in lots of it, to help the tank settle and have enough plants. Don't think of getting CO2 until you've come through the apprenticeship. I have been keeping tanks for 3 years and haven't yet moved onto CO2. Add some Indian Almond leaves – cheap on eBay– for the cories. Whatever people say, I think it helps a beginner to use simple test strips, just to see if the nitrites / nitrates are OK. Floating plants to really help reduce stress. for fish. And what Tiger Tim said. You have very few fish so they need very little food. Distract the Molly at one end with a couple of flakes, and put in a very small amount of frozen daphnia for the other fish at the other end. When in doubt change water. It always helps. Keep on asking for help.
First two thoughts: too much light, not enough clean-up crew. For light you can either reduce the intensity, add some more floating plants to cast shade, or both of those things. I would not decrease the photoperiod - anything reasonable (10 hours per day or less) will be fine - lighting intensity is the big algae driver in my experience. You have lots of snails, so give them some amano shrimp friends - for a tank your size you can easily start with two dozen amanos. They will chow on your soft stringy green algae. Your green stuff (including the algae!) is growing and green, so whatever your fertiliser routine is seems fine - I wouldn't mess with that until you have the lighting sorted out.
Thank you so much, any and all advice is truly appreciated.

At the moment I have duckweed (which I hate!) and water lettuce covering around 50% of the tank cover.

I use TNC complete, but only every few weeks.

I clearly need to do a larger water change each week so that is one thing I will start from now. I have been doing a 10litre change weekly, will up this to 30/40 litres.

My light is on for 10 hours a day. It isn't a light that is adjustable - I am happy to purchase a new one.

I will get some shrimp and infian almost leaves.

I have test strips and I also have a seachem nirtrate alert hanging in the tank at all times.
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Hi Polly
This would be my plan of action...if you are going to move the aquarium!
Remove the white sand, it is just a reflector for your lighting causing algae, add black sand or grey.
Reduce the lighting to 7 hours per day at a new start-up or when implementing a change.

Water lettuce covers around 50%; although a good method for reducing lighting and removing excess nutrients they can be too efficient....draining the aquarium of Nitrate and other essential nutrients for other plants.
Implement this Tutorial below.

You need 4 female Mollies to keep the male from harassing the lone female.....but then this would result in molly fry!
Add the fertilizer 3 or 4 days after the water change.
Clean your filter when doing water changes.
I don't mind having fry, so will get some more molly but not until things have settled.

When cleaning the filter - how do you do it. I've done it once, I sort of rinsed the media in the water I had removed from the tank.
I'm afraid some advice will contradict. Personally I'd be careful of black and dark sand as I find it hard to find a natural type that works well, others may know a reliable brand. I'd use leaves to partially cover the sand. And get an adjustable light, that will really help.
I have ordered some indian almond leaves, and some amino shrimp - due to price I've just got 10 for now.

I won't be moving the tank just yet but when I do I will look at getting a different adjustable light, and perhaps some different sand.

I will also look at possible swapping out the driftwood for rocks.

Plant wise I did buy pennywort but it hasn't thrive at all!

I tried to get rid of the duckweed before bit it all came back.

I will try again, I have to remove the water lettuce and rinse the roots and then I'll need to literally look in the filter and cracks and crevices as it is beyond prolofic!
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Hi Polly, sorry you’ve really had a rough time of it since setting up.

There’s been lots of great advice already provided, all of which such be considered.

My two pence would be as follows.

Rip it down and start over, nice and slow.

Start out with just a low tech planted tank and some clean up crew.

Give it several months of getting used to growing plants, learning how lighting, fertiliser and maintenance effect your tank.

Once you have some stability I’d then start adding some small community fish.

Stay away from live bearers they just become problematic and success in this hobby relies heavily on good experience and having fun with your tank.
I appreciate the above might not be feasible. But with a tank move imminent anyway it seems like a good opportunity to reset and start again taking things a lot slower and learning each step that you towards having the fish tank you want and deserve.
Hi Polly, sorry you’ve really had a rough time of it since setting up.

There’s been lots of great advice already provided, all of which such be considered.

My two pence would be as follows.

Rip it down and start over, nice and slow.

Start out with just a low tech planted tank and some clean up crew.

Give it several months of getting used to growing plants, learning how lighting, fertiliser and maintenance effect your tank.

Once you have some stability I’d then start adding some small community fish.

Stay away from live bearers they just become problematic and success in this hobby relies heavily on good experience and having fun with your tank.

I can't say I am not tempted. But I have a bloody attachment to the remaining fish I have :(

The only other option for me, would be to set up my old tank which is a 70L with the fish and then work on my new tank as their future home.

I still have my old filter, and light and thermometer so I could do that?
Also unrelated but I'm thinking of getting a water pod 2 or similar to have filtered water straight from my tap, would that help my aquarium as well? Apparently it is like getting bottled water from your tap.
Understandably you’re attached we all become attached to our fish and yes you could set up a temp home using existing filter or the media at least.

Forgive my bluntness. I see the world a little more black white than most. Just remember that the attachment you have could lead to more deaths if you’re having tank troubles.

Regards the filter I’m not sure it would help they’re designed for drinking and not fish keeping.

Using rain water, or tap water reconditioned or tap water / RO water 50/50 is your best option.
Although people can and do run tanks on dechlorinated tap water just fine.

Or you can tell yourself that you’re not going to throw in the towel and work hard to get your tank back on track.

Adjust you’re lighting if required
Adjust fertilisation
Scrub and siphon algae daily followed by a waterchange to help rid your tank of it
Adjust the amount you’re feeding if it’s too much
Maintain your filter
Ensure water-changes are with dechlorinated tap water that meets the same temperature.

These are all steps you could take towards getting your tank back on track.
If you’re going to make changes, remember that it may take time for the tank to adjust to the new changes. I suggest limiting the changes to two or three and see if they have an impact. If you change too many things at once, you will not know what has had a positive or negative impact on the tank. Have you got a current full tank photo?
If the tank is shot, it's shot, nothing you can do about it. Move the fish into the 70 as a holding tank and take your leisurely time to enjoy setting up the big one properly. I'm currently there with a Betta and a couple freshwater prawns, and as long as you WC, have plants there, and feed them, they don't care about aesthetics. In the long run, being comfortable with the hobby is the best thing you can do for their health. Plus, if you just want to focus on fish health, it's rather easier than aesthetics + health. Just throw in a big wad of java moss and floaters, change weekly, they'll be cool.

And then, spend a couple of months planning a scape! Figure out what went wrong, what you'd change. Snoop around journals and threads here and on the rest of the internet. Maybe run some trials... And then set up a tank for success and maybe a couple of years' worth.
You seem to be getting a lot of contradictory advice in this thread, which is unusual for UKAPS, we usually all sing from a similar hymn sheet, so here's my 2p for what its worth:

Firstly there doesn't appear to be a lot wrong with your tank currently from the images above, sure there is some algae (most people get BGA below the sand surface at the front - so don't worry about that) , but your plant health doesn't look that bad - your tank is a way off an unrecoverable position. I suspect the problem lies with a lack of consistency with maintenance and management of the tank. We could do with some more images including a FTS (full tank shot) and a shot of the surface too to assist further.

Secondly don't rip the tank out and start again, you'll learn little from doing that, and likely just end up in the same position in six months time. You have a nicely matured substrate and that is key to a stable tank, so keep that no matter what, even if you do decide to rescape. My order of business with your tank would be as following:

  1. Give it a through clean out - siphon out any obvious detritus build up, and manually remove and siphon out as much algae as possible from the glass and hardscape.
  2. Remove any notably unhealthy or algae covered leaves from the plants, and trim stem plants and replant the tops as necessary.
  3. Do several large water changes in a row. I'd say 50% every couple of days for a week with fresh dechlorinated water. Then keep on top of water changes - 10 litres isn't nearly enough if you want to promote a healthy and algae free environment, even on a low stocked low tech tank. I'd consider 20%-50% (so 32-80 litres per week) - you can't change too much water!
  4. Dose your TNC Complete consistently with each water change (including those mentioned on point 3) as per the bottle, as suggested by @tigertim - a lack or absence of nutrients will lead poor plant health and promote algal growth, and your floating plants will suck up lots of nutrients as @GHNelson points out, due to their access to atmospheric CO2.
  5. Ensure you are getting good gas exchange on your tank by making sure the filter outlet is creating as much surface agitation as possible. You want a good strong surface ripple, and better still some breaking of the surface layer as the water comes out (it would be good to see an image of how this is working currently).
  6. Add some clean-up crew - Ramshorns snails and cherry shrimp are the best options - these will help minimise new algal growth, and give you even more interesting things to look at in your tank.
In terms of stocking, livebearers can be a bit of a pain as they produced so many young - personally I would go with other fish in the longer term.

Where did you get your fish from? I wouldn't rule out unhealthy stock as a contributor to your fish losses if from a local shop, but certainly the lack of water changes will not have helped. I would also consider live food culturing for your fish - you can grow daphnia in big tubs outside, or get a grindal worm culture going - both very easy to do) - live food will help condition your fish and make them more robust against disease.
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@Wookii has made a great point there. We have all given you contradictory advice and I can only apologise for that Polly, you’re head must be in a spin.

As already mentioned. Get some pictures up of your tank face on.
And let’s get you back on track having learnt something from the experience.
Saving your tank rather giving up on it will be far more rewarding.
I am going to respond properly later but here at some photos of the tank face on. I also have two air stones running at either end of the tank.


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