Max Stocking Levels, I Mean Max

[fry_lover]

Ok, i am upgrading my 170 litre (38 Gallon-UK) community tank to a 300 litre (67 gallon-UK) at the weekend

Currently in the 170 litre i have approx 109" of fish and according to Practical Fish Keeping the total max is 74" so obviously i am over stocked. The fish include; corydoras, small tetras, small gouramis, guppies, platies, swordtails and danio's.

Its massively planted and the nitrate in this tank is about 5-10 mg/l even after 2-weeks of no water change. My tapwater nitrate is always about 25mg/l and the Nitrate in my Cichlids tanks usually gets to about 50-60mg/l before a water change

Nitrite and Ammonia are ALWAYS undetectable and i think i have had about 3-4 fish deaths in this set up in the last 6-months or so

As the livebearer fry have been getting bigger i have either been giving them away or selling them to keep the population down.

My main points being

1. What formula's do you use for stocking density

2. With my fish selection, including lots of Corydoras feeding off the bottom am i able to slightly go ABOVE recommend doses more safely than some other choices of fish, such as cichlids?

3. My plants are really flourishing, no co2 and i am in a very hard water using about only 1.5 watts-per-gallon, i believe the high fish stocking has helped this according to some plant experts i have been in touch with

4. My tank is x1.5 times over stocked according to the figures (i have 109" and the max is supposed to be 74") and it looks BUSY but it really doesn't look that over stocked to me (perhaps coz of the Cory? the Cory account for about 25% of the total stock level in inches. I have quite a few of them!!!

5. Its a very lively, active tank, all fish showing good colouring, none of these fish have had a sign of illness, and unlike other community tanks i have had in the past i can watch this tank for 1-hour straight and see no "flicking" or "rubbing" against plants / rocks

I am x1.5 times over stocked, when i upgrade to the 300 litre tank, the max is supposed to be 132" and i am thinking i will still slightly over-stock as i want some more tetra's and also some baby bristlenose. I was thinking to perhaps go to about x1.25 over the max? Not as high as x1.5 over the max

Filtration is just a Aqua Pro 1 (small external, only 3-litre volume and 600 litres / hour) AND x2 Fluval 1 at the other end (tiny internal filters) of tank, more for water flow than filtration.

I used to do 30-35% water change per week, i have reduced that to about 15-20% a week as the nitrate got so LOW in the tank (about 5mg/l) at one point, that i become concerned as the water going in was 25mg/l nitrate (from tap)

SORRY for such a long post, would really appreciate some knowledgeable peeps giving me some feedback and tips.

 

[Aphotic Phoenix]

The Corydoras might be eating any leftover food...but they are producing waste products themselves which is still a major issue. They are also contributing to the CO2 load etc. Just pointing out that adding fish does not somehow increase the number of fish you can keep safely.

Now that being said...I consider several factors when I decide how and how much to stock my tank including activity level, territory and swim space, max size of each individual species, preferred swim location in tank (top, middle, bottom), diet/metabolism, frequency of water changes, filtration, etc. Plus there are some common sense things too...if your fish tank looks like a stock holding tank at your LFS then yes you are most likely severely overstocked.

Unfortunately there is no prefect formula for proper stocking ratio. Do remember this though...the more fish there are, the higher the risk to the fish if something goes wrong mechanically in the tank (power outtage, filter breaks, heater etc)

 

[Tokis-Phoenix]

I think you are taking the 1inch of fish per gal rule too literally/seriously. I'll put it like this: There are no accurate "formula's" for calculating how many fish you can put in your tank that are guarenteed to work. Knowing how many fish you can put in your tank and how many is decided on many factors, and a great deal of it simply comes down to experience and understanding/knowing your fish and how they behave and their individual requirements/care etc.
I will try to help you with your stocking, but first i need more info on your situation;

a. What are the exact dimensions/measurements of your 170 litre tank?
b. How long has the tank been set up and how was it cycled exactly?
c. What are the exact types of fish you have and their numbers? How large are each type of your fish currently roughly?